Method for preparation of purified glycerides; and, products

ABSTRACT

A method of preparing purified ester compositions is provided. The process can be utilized to isolate and purify monoglycerides and propylene glycol monoesters, to advantage. It can also be used to isolate preferred diester products. The invention also concerns equipment for conduct of the processes, provision of preferred food additives, and provision of preferred food industry compositions. The process generally involves use of liquid-liquid extractions, to advantage.

CROSS-REFERENCE TO RELATED APPLICATION

[0001] The present application is a continuation-in-part of U.S.application Ser. No. 08/614,468 filed Mar. 13, 1996. The completedisclosure of Ser. No. 08/614,468 is incorporated herein by reference.

FIELD OF THE INVENTION

[0002] The present invention relates to ester production and isolation.In one type of application, it particularly concerns methods ofisolating purified monoglycerides from crude monoglyceride mixtures. Inanother, it concerns isolation of purified diglycerides. In preferredapplications, liquid-liquid extraction is utilized to advantage. Thetechniques can also be applied to isolate related materials, such aspropylene glycol monoesters and derivatives of monoglycerides.

BACKGROUND

[0003] Monoesters such as monoglycerides are widely used food additives,for example as emulsifiers and dough conditioners. In general, suchmaterials comprise esters of fatty acids. The term “monoglyceride”specifically refers to a derivative of glycerol, i.e., a glyceride, inwhich only one of the three available hydroxy groups of the glycerolmoiety is esterified, hence the prefix “mono-”. By “esterified” in thiscontext, it is meant that the glycerol moiety forms the alcohol residueof an ester (typically with a fatty acid residue).

[0004] In general, crude monoglyceride mixtures are made from reactingnaturally occurring triglycerides, often obtained from oil seedprocessing, with glycerol. Such reactions generate a mixture ofmonoglycerides, diglycerides and triglycerides. Limitation onmonoglyceride production, via this approach, is generally controlled by:(1) solubility of the glycerol in the reaction mixture; (2) the overallequilibria statistics; and, (3) time. Typical commercially availablecrude monoglyceride mixtures made using this approach include ratios ofmonoglyceride:diglyceride:triglyceride (by weight) of about 45:45:10; orabout 60:35:5, depending on processing conditions used.

[0005] In many instances, it is preferred to utilize more purifiedmonoglycerides. That is, crude monoglyceride compositions or mixturesare purified for at least partial isolation of the monoglycerides fromthe diglycerides and triglycerides. In general, monoglyceridedistillation has been the most widely utilized technique for suchpurifications. Typically the crude monoglyceride mixture is distilledunder vacuum, in a short path distillation process. The distillategenerally comprises greater than 90% (by weight) monoglycerides. Theremainder generally comprises diglyceride. During the process, themonoglycerides are generally heated to at least 200° C.

[0006] In other processes, supercritical extractions have been used forisolation of monoglycerides. These generally concern extraction underpressures greater than atmospheric (typically 30-80 atmospheres) andtemperatures in excess of 100° C. (typically 110° C. or so). Theygenerally concern extractions with low molecular weight hydrocarbons,such as propane. Such approaches are generally prohibitively expensive,for application on a large scale.

[0007] Closely related materials to monoglycerides include propyleneglycol monoesters (PGME's). Such materials are generally made fromesterifying propylene glycol with naturally occurring oils, i.e., fattyacid mixtures, resulting in a mixture of monoesters and diesters.Generally the monoesters are isolated by distillation. Such materialsare also widely utilized as emulsifiers and as dough conditioners in thefood industry.

[0008] In certain food applications, diglycerides are used. For example,diglycerides may be used as components of shortening and as fatreplacers. As a result, in some instances, it is desirable to isolatediglycerides in a purified form, from a crude mixture. Techniques toaccomplish this are described herein. Herein the term diglyceride refersto a derivative of glycerol in which two of the three available hydroxygroups of the glycerol are esterified; and, the term “triglyceride”refers to a derivative of glycerol in which all three available hydroxygroups are esterified.

SUMMARY

[0009] Methods for preparing purified ester compositions from crudeester compositions are provided.

[0010] According to one aspect of the present invention, a method isprovided for preparing a purified target ester-containing foodcomposition. Herein the term “target ester” is meant to refer to theselected ester or mixture of esters, of a crude mixture of esters, to beisolated for purification. For example, if the crude ester compositioncomprises a mixture of glycerides and it is desired to isolatemonoglycerides, the target ester fraction comprises the monoglyceridesfraction or component of the mixture. Herein the term “food composition”in this context, is meant to include any material or component that isin a suitable form to be used as a food additive and/or in the finalfood product or food mixture.

[0011] In general, the method of preparing a purified target estercontaining food composition comprises providing crude ester compositionwhich at least includes:

[0012] 1. at least one target ester; and,

[0013] 2. at least one contaminating ester.

[0014] Herein the term “contaminating ester” is meant to refer to theester components of the crude ester composition which do not comprisethe target ester.

[0015] In general, the target ester will be selected from the groupconsisting of: (a) C₃-diol target esters of fatty acids; (b) C₃-trioltarget esters of fatty acids; and, (c) mixtures of the previous two. Intypical instances, the target ester will comprise either monoester(s) ordiester(s), or mixtures of the two.

[0016] The contaminating ester will also typically be selected from: (a)C₃-diol contaminating esters of fatty acids; (b) C₃-triol contaminatingesters of fatty acids; or, (c) mixtures of the two. Typically thecontaminating esters will include triesters, and in some instances willalso include diesters or monoesters. For example, if the purpose is toisolate purified monoesters from a composition also comprising diestersand triesters, the target ester will comprise the monoester and themixture of diesters and triesters will comprise the contaminatingester(s). On the other hand, if the intent is to isolate diesters fromsuch a mixture, then the target ester will comprise the diester mixtureand the contaminating esters will comprise the triesters (and mostlikely also the monoesters). Of course in some instances, both apurified monoester stream and a purified diester stream is desired. Insuch cases each is a target ester (at least relative to the other).

[0017] According to the process, the step of extracting the crude estercomposition is conducted with an aqueous alcohol phase that is tuned toselectively extract into the extracted phase a first of: (1) theselected target ester(s); and, (2) the selected contaminating ester(s),relative to a second of: (1) the selected target eater(s); and, (2) theselected contaminating ester(s).

[0018] Herein the term “selectively extract”, when used in this context,means an extraction which results in a higher ratio, by weight, of theselected ester(s) versus the non-selected ester(s) in the extractantphase, relative to the original phase from which extraction occurs. The“selected ester(s)”, of course, may be either the target ester(s) or thecontaminating ester(s). Thus, a selective extraction in this context isan extraction which, at the same time as extraction, results in somelevel of purification of the selected target ester(s), with respect tothe contaminating esters.

[0019] In certain preferred operations, after the extraction, theextractant phase, upon separation, is treated with a crude triglyceridephase. Typically this is a triglyceride wash. The effect will be topurify the extractant phase, by extracting into the triglyceride washthose ester materials preferentially soluble therein. Thus, as a resultof the treatment or wash, there is generated a further purifiedextractant phase and a triglyceride phase. When such is the case,generally the process will include a step of separating the purifiedextractant phase from the triglyceride phase, the purified extractantphase in some instances including therein the target ester. When such isthe case, the target ester can then be separated from the solvent, toform the resulting food composition. This material may then bepreferentially introduced into food products, as described hereinbelow.

[0020] In alternate applications, the extractant phase from the firstextraction will include therein contaminating ester, that may bealternatively used or recycled, and the raffinate phase will includetherein the target ester. The target ester, in the raffinate phase,would then be used in food.

[0021] The process is typically and preferably used to purify crudemonoester compositions including C₃-diol or C₃-triol monoesters of fattyacids. The term “C₃-diol” as used herein is meant to refer to a 3-carbonchain dihydroxy compound, typically wherein each hydroxy group is on aseparate carbon. The term “C₃-triol” as used herein is meant to refer toa 3-carbon chain trihydroxy compound, typically wherein each hydroxygroup is on a separate carbon atom. Typically C₃-diol monoesterspurified according to the present invention will comprise propyleneglycol monoesters; and, C₃-triol monoesters purified according to thepresent invention will comprise monoglycerides. Analogously, the targetester could be a diester of either a C₃-diol or a C₃-triol, for examplea diglyceride mixture.

[0022] Typically, crude ester compositions to be purified according tothe present invention will comprise crude ester compositions made fromreactions of naturally occurring triglycerides, such as palm oil, canolaoil, soybean oil, sunflower seed oil, or beef tallow or various fats.The triol monoesters are typically prepared by reacting such naturallyoccurring oils or fats with glycerol; and, the C₃-diol crude monoester(or diester) compositions are generally prepared by reacting naturallyoccurring triglycerides with propylene glycol. The term “naturallyoccurring” in this context and in connection with identifying oils orfats, is merely meant to refer to oils, fats or mixtures of oils and/orfats that can be isolated from natural products; for example from cropsor animal processing. It is not meant that the materials are in theirnatural form, but indeed typically will have been isolated through someform of processing. Also, it is not meant by the term “naturallyoccurring” that the isolation could not have been from a man-made hybridplant or animal, or genetically altered plant or animal.

[0023] It will also be understood that techniques according to thepresent invention can be utilized in association with oils/fats thathave been modified from their natural form in some manner, for examplethrough hydrogenation or various esterifications. Herein the term “oil”is differentiated from the term “fat” in that oils are generally liquidat room temperature and fats are generally solid or semi-solid at roomtemperature. Both are triglycerides and will generally be treatedanalogously in processes according to the present invention.

[0024] In some applications, the purification includes a step of adding,to the crude monoester composition to be purified, an effective amountof triglyceride (s) to form a primary extraction triglyceride-containingphase. In this context, the term “effective amount” is generally meantto refer to an amount of triglyceride(s) which will facilitate retentionof diglyceride(s) in a “primary extraction triglyceride-containingphase” during the extraction. Typically and preferably the amount oftriglyceride(s) addition will be about 30 to 200 parts by weight per 100parts crude monoester, especially when the triglyceride(s) comprises thesame triglyceride(s) (or is derived from the same triglyceride) as wasused to form the crude monoester composition. Most typically 45 to 100parts by weight per 100 parts crude monoester will be used.

[0025] Alternatively, one can characterize certain processes accordingto the present invention in terms of the composition of the mixture fromwhich the monoglycerides are extracted. The mixture would generallycomprise at least 30%, by weight, triglycerides, as a result of thetriglyceride addition to the crude monoglyceride prior to extraction. Ingeneral, the composition would comprise a diglyceride content of nogreater than about 2 times the monoglyceride content, by weight. Thislatter would also typically be true of the crude monoglycerides to beprocessed. Preferably, the mixture from which the extraction ofmonoglycerides occurs, has a diglyceride presence which is less than thetriglyceride presence, by weight, generally as a result of thetriglyceride additions to the crude monoglyceride mixture.

[0026] For typical applications, to isolate either monoesters ordiesters, when triglycerides are added, the amount of triglycerideaddition will be such that the result will have, by weight, moretriglycerides than diesters, by weight. When the diester is diglyceride,then the result will be more triglycerides than diglycerides by weight.When such an addition of triglycerides is conducted, the effect may besuch that the amount of monoester in a composition, when the extractionoccurs, is, in some typical applications, as low as about 20% by weight,based on total weight of ester in the crude ester composition. Similarlywhen such a dilution occurs, the amount of diester, which typically inthe crude composition (before dilution by triglyceride addition)purified would be present at a level of at least 25% by weight, may bediluted such that its presence is as low as about 15% by weight, basedon total weight of esters in the phase which is extracted.

[0027] Typical, preferred, processes according to the present inventioncomprise a step of extracting the primary extractiontriglyceride-containing phase with an alcohol/water extractant.Typically and preferably the alcohol is a low molecular weight (C₃ orless) alcohol. Preferably it is an alcohol of a straight chainhydrocarbon compound. Typically it is a monohydroxy compound, mostpreferably with a terminal —OH group. Most preferably it is ethanol.Most typically, especially when the alcohol is ethanol, thealcohol/water extraction will comprise, by weight, at least 60% alcoholand no more than about 90% alcohol. Also, typically it will contain10-40%, by weight, water. Most typically it will include about 70-85%alcohol, and 15-30% water, by weight. Such systems will generally bequite selective, for extraction of monoesters from the crude monoestercomposition, with substantial selectivity relative to extraction ofdiesters or triesters. Such systems will also generally have a highextraction factor for monoesters, allowing use of relatively lowextractant flow rates.

[0028] Preferably, after the step of separating, the alcohol/waterextractant phase is treated for isolation of monoester compositiontherefrom. This will typically involve a step of removing thealcohol/water extractant from the extractant phase, for example bydistillation of the alcohol/water. Preferably, regardless of thespecific technique used, the step of isolating is conducted without astep of distilling the isolated monoester(s).

[0029] In certain preferred operations according to the presentinvention, especially for monoester isolation, the step of providingcrude monoester compositions comprises providing crude monoglyceridecompositions. Crude monoglyceride compositions typically contain atleast 30% monoglyceride and at least 25% diglyceride, based on totalweight of monoglycerides, diglycerides, and triglycerides therein.Typically they contain no more than about 70% monoglycerides, by weight,based on total weight of monoglycerides, diglycerides and triglycerides,and they are typically purified to provide a purified monoestercomposition having a monoglyceride presence of no less than 85, based ontotal weight of monoglycerides, diglycerides and triglycerides in thepurified monoester composition. Indeed, typically the purificationprocesses will be practiced to achieve at least 90% monoglycerides, onsuch a basis, and in some preferred applications they will be practicedto provide at least 95% by weight monoglycerides in the purifiedmonoglyceride composition.

[0030] When the practice is with monoesters other than monoglycerides,for example PGME's, similar results can be obtained. However, typicallywith PGME's the compositions will also include some propylene glycoldiesters, as well as monoglycerides, diglycerides and triglycerides fromprocessing. In such instances, the purification will generally involveselectively retaining monoglyceride with the purified PGME, relative todiglyceride and triglyceride. However an alternative is providedhereinbelow, in connection with FIG. 5.

[0031] Preferably the step of extracting with alcohol/water extractantcomprises conducting a multi-stage counter-current extraction; typicallywith at least two stages and preferably at least three. Preferably theextraction is conducted at a temperature of at least about 60-80° C. andnot greater than 120° C., so that triglycerides present will be in theliquid phase and the alcohol/water solvent will generate only relativelylow pressures. Typically, the extraction with ethanol/water is conductedat about atmospheric pressure, and preferably at pressures no higherthan 5 atmospheres.

[0032] Preferred processes include a step of back extracting or washingthe alcohol/water extractant phase from the primary or first extraction.The step of back extracting or washing is preferably conducted with atriglyceride-containing phase, for further “tuning” of the purification,to reduce a presence of diglycerides that may have been extracted intothe alcohol/water extractant, during the primary extraction. The step ofback extracting or washing, then, can be referred to as a “wash” of theextractant from the primary extraction with a triglyceride-containingphase.

[0033] In some applications, the triglyceride-containing phase, from thestep of washing, is added to the crude monoglyceride mixture, as asource of added triglycerides for conduct of the primary extraction.Preferably the step of washing also comprises a multi-stagecounter-current washing; again typically having at least two stages,preferably at least three.

[0034] According to some aspects and applications of the presentinvention food additives are provided. In general, the food additivescomprise purified monoglyceride (or other ester) component isolated orpurified according to the present invention. In certain preferredsystems involving purified monoglycerides, the purified monoglyceride(monoester) component comprises at least 85% by weight monoglycerides(or monoester), based on the total weight of monoglycerides(monoesters), diglycerides (diesters) and triglycerides (triesters) inthe monoglyceride (monoester) component.

[0035] In general, typically when crude monoglyceride compositions areutilized, prior to addition of the triglycerides thereto, the crudemonoglyceride composition comprises, by weight, no more than 20%triglycerides, based on total weight of monoglycerides, diglycerides,and triglycerides in the crude monoester composition. Again, preferablyit contains no more than about 70% monoglycerides, by weight, based ontotal weight of monoglycerides, diglycerides, and triglycerides in thecrude monoglyceride composition. In general, when monoglyceridepurification is intended, the method can be characterized as beingconducted to achieve the isolation of purified monoester composition,having: a monoglyceride presence of no less than 85%, based on totalweight of monoglycerides, diglycerides and triglycerides in the purifiedmonoester composition; and, a diglyceride-to-triglyceride weight ratio,in the purified monoester composition, of no greater than 1:1.

[0036] The present invention also concerns provision of a processingfacility for purifying crude compositions. The processing facilitygenerally includes a primary counter-current extractor as described; asecondary counter-current extractor as described; fluid directionconduit arrangements for preferred cycling and direction of materials;and, a source of triglyceride and a source of crude composition (forexample, crude monoester composition to be purified) constructed andarranged as necessary, for provision of preferred operations. In someinstances, additional extractors may be used.

BRIEF DESCRIPTION OF THE DRAWINGS

[0037]FIG. 1 is a schematic presentation of a process and equipment forpractice of the process, according to a first described embodiment ofthe present invention.

[0038]FIG. 2 is a schematic presentation of a process and equipment forpractice of an alternate embodiment, to that described in connectionwith FIG. 1.

[0039]FIG. 3 is a schematic presentation of a process and equipment forpractice of the process described in connection with FIG. 2, FIG. 3 alsoincluding process steps and equipment for isolation of a purifieddiglyceride stream.

[0040]FIG. 4 is a schematic presentation of a process and equipment forpractice of an alternative process to that described in connection withFIG. 3.

[0041]FIG. 5 is a schematic presentation of a process and equipment forpractice of the process, according to a preferred application forisolation of a purified propylene glycol monoester stream.

DETAILED DESCRIPTION

[0042] The present invention concerns methods, techniques and equipmentfor purifying or isolating materials such as monoglycerides,diglycerides, and propylene glycol monoesters (i.e., target esters),from crude ester mixtures containing related diesters and relatedtriesters (i.e., contaminating esters). The techniques describedgenerally utilize preferred liquid-liquid extractions, to facilitate theprocess. Most preferred practices are conducted under conditions inwhich the monoester to be isolated (or any other isolated target ester)is not distilled at any point in the process. Preferably it is conductedwithout subjecting the crude ester composition, after formation, totemperatures in excess of 140° C. and/or pressures in excess of about 5atm. Typically the processes described herein can be practiced withoutsubjecting the crude ester composition, after formation, to temperaturesin excess of 120° C. and/or pressures in excess of 3 atm. Also,typically, (at least in most preferred applications) no large amounts ofmaterials such as non-alcohol solvents (propane, butane, hexane, ethers,ketones etc.) are used, during the step of extracting from the crudemixtures. Preferably none of these materials is used. Herein the term“no large amounts” in this context is meant to refer to no more thanabout 15-20%, by weight, of the referenced solvents.

[0043] I. Materials Purified

[0044] Glycerol is a 1,2,3-trihydroxy propane, or propylene triol. It istypically obtained from hydrolysis or alcohol reaction, of naturallyoccurring triglycerides, during fatty acid production. Propylene glycolis a 1,2-dihydroxy propane (1,2-propane diol). Propylene glycol istypically obtained from hydrolysis of propylene oxide. Techniquesaccording to the present invention were developed to facilitateisolation and purification of target esters such as monoesters and/ordiesters of such materials, from crude mixtures containing themonoesters and diesters (and in some instances triesters). Theparticular monoesters of greatest interest, are fatty acid monoesters,for example propylene glycol or glycerol monoesters of fatty acids.Herein the terms “isolation and purification” when utilized in thiscontext, and in similar contexts, are not meant by themselves tospecifically refer to some particular level of purity of the isolatedtarget ester material, for example, monoester, other than an improvedpurity relative to the crude mixture. However, in typical applications,the technique can be utilized to obtain monoester purities of at least85% (by weight), and usually preferably to obtain purities of at least90%, relative to contaminating diesters and triesters (i.e.,contaminating esters). In some specific applications, monoester puritiesof 95% or greater can be obtained.

[0045] It is foreseen that techniques according to the present inventioncan, for example, be utilized to isolate and purify a variety ofmonoesters, from crude mixtures of the monoesters with related di-(and/or tri-) esters. For example, according to the present invention,monoesters isolatable using the techniques typically comprise esters ofC₃- or C₄-diols or triols, wherein each hydroxy group is on a separate,isolated carbon in the 3 or 4 carbon group. Typically, the applicationswill cover esters wherein the ester group is a straight chainC₃-multi-hydroxy compound. Typically the compounds will be monoesters ofdihydroxy- or trihydroxy-substituted propane or butane.

[0046] Herein the term “fatty acid” is meant to refer to acids having atleast 4 carbon atoms, typically, but not necessarily, 12 to 20 carbonatoms, and includes saturated and unsaturated fatty acids.

[0047] The fatty acids of greatest interest to the present invention arethose derived from naturally occurring mixtures of oils or fats (orfatty acid derivatives) found in such fats and oils as: palm oil;soybean oil; canola oil; peanut oil; cottonseed oil; coconut oil; and,beef tallow. (The term “naturally occurring” in this context is meant toinclude reference to products from processing man-made hybrids orgenetically altered plants or animals, as well as natural ones.) Suchmaterials generally include mixtures of saturated and unsaturated fattyacid derivatives (fats) and primarily include fatty acid derivativeshaving an even number of carbons in the fatty acid backbone. Theytypically include predominately C₁₀ or greater acids, typically C₁₂ orgreater. Herein when the term “C₁₀” is used in this context, it is meantthat the carbon chain of the acid fragment, including the acid carbon,has 10 carbon atoms in it.

[0048] Reaction mixtures to be purified according to the presenttechniques can be made in a variety of manners. Typically they willcomprise mixtures of mono-esters and di-esters, and in some instancestrimesters, of a short chain di-hydroxy or tri-hydroxy compound. Adesired result of the purification, when monoester isolation isintended, typically includes generation of a mixture comprising at least85%, and typically at least 90%, by weight, monoester (relative tocontaminating diester and, if present, triester), and more preferably atleast 95% by weight, from a mixture comprising at least 30% andtypically no more than about 70-80% (and sometimes no more than 60%) byweight of the monoester, typically about 35-65% by weight, based ontotal weight of monoester plus diester (and, if present, triester).

[0049] Although crude mixtures of monoesters to be purified according tothe present invention may be obtained in a variety of manners, typicallythey comprise the reaction product of 3- or 4-carbon chain di- ortri-hydroxy compound, with naturally occurring fatty acid estermixtures, typically triglycerides. Most typically, the crude mixtureswill comprise the reaction product of either glycerol or propyleneglycol with a naturally occurring triglyceride mixture such as palm oil,soybean oil, canola oil or sunflower oil. In some instances modifiedoils (such as partially hydrogenated oils or esterified oils) may beused.

[0050] Typical crude glyceride mixtures used in processes according tothe present invention, especially for monoglyceride purification andprior to any triglyceride phase addition, will include monoesters anddiesters in a weight ratio of about 0.75:1 to about 2:1 (mono:di), andin some instances may include a minor percentage (for example, up to10-15% by weight) of triester, before any triglyceride addition tofacilitate extraction. Typical crude monoglyceride mixtures, which willbe purified using techniques according to the present invention, priorto any triglyceride-phase addition, comprise products havingmono:di:triesters present in weight ratios of about 45:45:10 or about60:35:5. These are the common crude monoglyceride mixtures, made inindustry.

[0051] It is foreseen that crude monoglyceride mixtures containingvariations from these amounts will be purifiable with techniquesaccording to the present invention. However, the techniques weredeveloped in a manner calculated to especially facilitate purificationof such mixtures, because they are the types of mixtures prevalent inindustry as crude monoglyceride mixtures.

[0052] When techniques according to the present invention are utilizedfor purification of monoesters such as propylene glycols, i.e.,monoesters other than monoglycerides, generally analogous conditions andlevels of purification to those described above with respect tomonoglycerides are achievable. In such context, however, the weightpercent of monoester stated will generally be based upon total weight ofmonoester, diester, and triester present, regardless, for example, ofwhether the diester and triester are glyceride esters or esters of theparticular alcohol of concern, or a mixture of both. The latter will betypical, since, for example, propylene glycol monoesters are typicallyprepared from triglyceride and thus crude propylene glycol monoestermixtures will include propylene glycol diesters, monoglycerides,diglycerides and triglycerides.

[0053] II. Other Characterizations of Preferred Processing and Purity

[0054] A. Purity

[0055] In general, as explained above, techniques according to thepresent invention were generally developed to provide preferred overalllevels of target ester purity, for example with respect to purifiedmonoglycerides, in advantageous cost-effective manners. During thecourse of the study, however, it was discovered that while the absolutelevel of purity of the purified target ester (for example monoester) wasof great importance, it was not the only factor of interest with respectto preferred products. In particular, it was found that in someinstances, preferred products were obtained if there was a focus atleast in part upon the content of the principal contaminating esters.

[0056] For example, as indicated above, when the material to be purifiedis a crude monoglyceride mixture, the mixture generally comprisesmonoglycerides, diglycerides, and triglycerides. During the studies, itwas found that preferred purifications would occur if, with respect tothe contaminating diglycerides and triglycerides, the purification wasconducted in such a manner that the diglyceride to triglyceride ratio,by weight, was reduced to no more than 1:1 (and typically less), andtypically and preferably to less than 1:3. Since crude monoglyceridemixtures generally contain greater percentage of diglycerides thantriglycerides, by weight, by the above, it is generally meant that theprocess (for monoester purification) should be conducted in such a waythat focus is on diglyceride removal/reduction.

[0057] In the same context, and as part of the same evaluations, it wasobserved that in general preferred purified monoglycerides not onlycontain at least 85% (and preferably at least 90%) by weightmonoglycerides, but also have a monoglyceride-to-diglyceride ratio, byweight, of at least 40:1 and preferably at least 70:1. Again, typicallyand preferably, the majority of the contaminants in the purifiedmonoglycerides, by weight, in such systems is preferably triglyceride(as opposed to diglyceride).

[0058] B. Processing

[0059] As will be apparent from the following discussions and examples,a variety of techniques have been developed for characterizing preferredsteps of processing. Some of the more significant are as follows:

[0060] 1. Loading:

[0061] In general, processes according to the present invention will notbe considered preferred or particularly effective unless the loading ofthe ester (for example, monoester) to be purified in the polar phase orextractant, is substantial. That is, with techniques according to thepresent invention, one is not only trying to obtain high selectivityduring the extraction so that good purity results, but one is alsoseeking simultaneously a relatively high loading or at least substantialloading, so that the process is efficient. If loading is too low, theprocess will be commercially undesirable since high amounts ofextractant would be needed. In typical preferred processes according tothe present invention, including under the conditions described hereinbelow, one can achieve loading of the monoester(s) in the extractantduring the extracting process of at least 10 grams (g) per 100 gextractant, and typically loadings of at least 15 g per 100 g extractant(or more) are obtained. The term log monoesters per 100 g extractantrefers to the load in the extractant phase leaving the extraction step,for example at line 55, FIG. 1.

[0062] 2. Selectivity:

[0063] Processing according to the present invention can becharacterized with respect to the selectivity of the extraction. Whenmonoester purification is involved, this can be phrased in a variety ofways including the extraction selectivity for the monoester over thediester; the extraction selectivity for the triester over the diester;and, the selectivity of extraction for the monoester over the triester,when the process includes purification of mixtures including monoesters,diesters, and triesters. In monoester purification, a selectivity ofparticular concern will be the selectivity for the monoester over thediester.

[0064] In general, selectivity (α_(1,2) of component 1 to component 2)is defined by the ratio, for the extractant phase to the raffinatephase, of the ratio of concentrations, by weight, of component 1 tocomponent 2. Thus, a is a ratio of ratios. From the examples givenbelow, it will be understood that selectivities for monoester overdiester of >5 and for monoester over triester of >50 can be readilyobtained with processing according to the present invention.

[0065] III. Methods of Purification—Generally

[0066] A. Monoglyceride Purifications

[0067] In general, crude target ester mixtures, such as crudemonoglyceride compositions, according to the present invention arepurified through liquid-liquid extractions. For example, monoglyceridevalues in the crude mixture are preferentially extracted into(partitioned into) an alcohol-containing phase. Theseparation/purification is facilitated by the following:

[0068] 1. Provision of sufficient water in the alcohol-containing phaseto provide desirable selectivity of extraction; for example,preferential extraction or partitioning of monoglycerides vs.diglycerides (or even triglycerides) into the alcohol phase; and

[0069] 2. Provision in the non-alcohol phase of a component tofacilitate solubility of diglycerides (and triglycerides) in that phase.Preferably this added component includes a triglyceride or atriglyceride mixture. Most preferably it is a naturally occurring foodsubstance and does not contain substantial amounts (greater than 20% andpreferably none) of non-functionalized organic solvent such as ahydrocarbon (propane, butane, etc.).

[0070] In general, purified monoglycerides, with monoester contents ofgreater than 90%, until now have been available commercially only asdistilled monoglycerides. Because of the low vapor pressure,monoglycerides can be distilled only under relatively high vacuum andrelatively high temperatures. This leads to a process which is ratherexpensive and which can lead to undesirable products. Unfortunately,distilled monoesters are also sometimes responsible for a bitter flavorin the finished product, limiting the level to which they can be added.

[0071] In many applications it is the monoester which is providing thedesired functionality, with the attendant diester being present only asan unwanted byproduct. A source of more highly purified, low cost,monoesters can be, therefor, generally provided by the presentinvention.

[0072] In certain applications, the diester is in fact a detrimentalcomponent, and a higher price is paid in order to get the more highlypurified, distilled monoester. In some instances, the presence of thediester is believed to modify the phase behavior of the monoester,interfering with functional activity.

[0073] It is true that some alternative purification processes have beencontemplated in the art. Fractional crystallization, which utilizesdifferences in melting points between the monoesters and othercomponents, is generally feasible only for products with narrowlydefined fatty acid profiles, such as fully saturated oil of IV<2, wherethe fatty acids are dominated by a single species such as stearine. Inthis context the term “IV” refers to the iodine value, which is anindicator of the degree of saturation. Products with a range of IV willtend to fractionate by IV, rather than by degree of esterification.

[0074] Supercritical extraction using an extractant such as propane hasbeen suggested as an approach to purification, but it is too expensiveto be commercially viable. In general, it requires relatively highpressures (>60 atm) and involves relatively low loading (typically <5 wt% fat in the extractant wherein the term “fat” refers to whatever fattyacid ester is in the extractant.) It is noted that use of a non-polarextractant in supercritical extractant involves extraction of the di-and trimesters away from the monoester and into the extractant.

[0075] Adsorption techniques, wherein the monoesters are adsorbed onto asolid support and are later desorbed into a solvent, may be feasible buttypically would require large amounts of resin, which can increase cost.

[0076] Until now, the use of liquid extractants in a viable system hasnot been developed or proposed. For example, low boiling hydrocarbonssuch as hexane could be envisioned to selectively extract the di- andtri-esters, leaving the monoesters behind. In practice, however, thehydrocarbon has generally had too great a solvency and typically alsoextracted the monoglyceride, often forming a single phase system. Asupercritical use of propane has been suggested as a method around theseproblems, but such an approach is impractical and is generally assertedto be prohibitively expensive. Alcohols or alcohol/water blends may alsohave been proposed to extract the monoesters, and leave the diesters andtriesters behind. These approaches would not generally be commerciallyfeasible, however, at least because in order to achieve the desiredpurity of the monoester, the solvent polarity would need to be adjustedto be quite high (large water content) so that the overall solubility ofmonoesters would be unreasonably low, resulting in excessive solventrequirements. A combined process, using a hydrocarbon and analcohol/water extractant, would also be impractical on a large scale formany processes, because the hydrocarbon competes too strongly for themonoglyceride, resulting in low extraction factors and becauserecovering both the hydrocarbon and the alcohol/water adds cost.

[0077] The proposed preferred processes of the present invention, usingan aqueous alcoholic extractant and using triglyceride fat/oil as asecond phase to remove the diester, are unique and advantageous, butseveral obstacles needed to be overcome to obtain a useful process. Forexample, use of liquid-liquid extraction was perceived ascounter-intuitive because the very nature of the desired product,monoesters, is that of an emulsifying agent. Such a product is used tostabilize emulsions of water in oil, such as triglycerides. The formingof a stable emulsion would prevent the operation of a liquid-liquidextraction system. The present process has worked satisfactorily inspite of this, although it is believed that low shear mixing will beuseful and desirable in commercial scale practice, to prevent or inhibitformation of undesirable emulsions.

[0078] Secondly, triglyceride is one of the contaminating products inthe crude monoglyceride stream, so intentionally adding triglyceride inorder to help purify the monoglyceride is counter-intuitive. However,adding triglyceride has proven to be very useful in reducing the levelof diester present in the final product, when the desired final productis the monoester fraction.

[0079] Thirdly, residual triglyceride in the product is not readilyremoved (compared to a low boiling hydrocarbon such as hexane). However,it is believed that an important factor in defining purity of themonoester product may be how low the diester content is, or the ratio ofmonoester to diester content, rather than the absolute level ofmonoester content, or even the level of triester if it is below athreshold amount. After all, the purified monoester is frequently addedto products along with triglycerides in the emulsified shortening. Thus,the purified monoester, in use, may well be mixed with triester, and itis generally removal of diester which is of greatest concern.

[0080] Indeed, in some applications, a product with a weight ratio of90/5/5 monoglyceride, diglyceride, triglyceride may well be superior infunctionality to one of 90/10/0. The greater difference in functionalitybetween the monoester (monoglyceride) and the triester (triglyceride) isbelieved to cause triglyceride to be less interfering in the ability ofmonoester to form mesophases, than would be the same weight of diester.

[0081] It is also noted that the amount of triglyceride required, tofacilitate the separation and purification, has been found to berelatively small. If, as an alternative to the triglyceride, ahydrocarbon, such as hexane, were to be used to facilitate theseparation, a typical concentration might be 5-10 wt.-% of di- andtriglyceride in the hexane. At this level, one might expect cosolventeffects, if any, to be relatively small and the system would behave as ahexane solution. Note that this corresponds to a system 0.7-1.5 mole %diglyceride in hexane, giving more than 65 molecules of hexane for everymolecule of diglyceride. If triglycerides were needed at the same molarlevel as the hexane, the required amount of triglyceride would be atleast 90 times, by weight, of the diglyceride stream or a concentrationof less than 1.1 wt % diglyceride in the triglyceride stream. However,in preferred embodiments of the invention, where the triglyceride streamis subsequently used to generate more monoglycerides, the maximum levelof triglycerides used (i.e., added) typically is only about 1.5-3 timesby weight of the diglycerides, and in other preferred embodiments it isexpected to be no more than 8 times by weight of the diglycerides. Thepreferred minimum level of added triglycerides is expected to be greaterthan about 1 time by weight the diglycerides. At these levels ofconcentration, significant cosolvent effects are expected, and thesystem would not be characterized as a triglyceride stream, but ratheras a mixture of di- and triglyceride.

[0082] It also might be expected that the diglyceride would act as astrong solvent to the monoglyceride, resulting in the ineffectiveextraction of the monoglyceride by the alcohol/water stream and leadingto poor yields. This, however, has not been found. Based on batchresults, it is anticipated that the extraction yield (extraction ofmonoglycerides into the alcohol/water extractant) in a countercurrentextraction train will exceed 90 wt % of the monoglycerides present inthe feed.

[0083] Typically and preferably the extraction process, for monoesterpurification, is conducted at about 60° C.-80° C., and not above 120° C.Also, typically and preferably it is conducted at about atmosphericpressure, and not above 5 atm. Also, typically and preferably thealcohol layer comprises 60-90% alcohol and 10-40% water, by weight. Mostpreferably it comprises about 70-85% alcohol, and 15-30% water, byweight. It is foreseen that typical preferred alcohol/water layers intowhich the monoglycerides are extracted will comprise about 75%alcohol/25% water, especially when the alcohol is ethanol. The typicaland preferred alcohol will be ethanol because of high selectivity, highloading, low cost and acceptable toxic character.

[0084] Preferably the triglyceride added to the crude mixture comprisesthe same triglyceride as is present in the crude mixture prior totriglyceride addition. That is, in typical instances the crudemonoglyceride mixture that is to be purified will have been made from atriglyceride mixture; and, the same type of triglyceride mixture whichwas used to make the crude monoglyceride mixture is the one added to theresulting crude monoglyceride mixture, prior to the extraction of themonoglyceride values into the alcohol/water feed, to facilitate theextraction. For example, if the process is used to purify a crudemonoglyceride composition isolated from soybeans, then preferably thetriglycerides added to the crude monoglyceride mixture to facilitate theextraction will be a crude mixture from soybeans, i.e., soybean oil,preferably with the same degree of hydrogenation. Advantages as a resultof this will be apparent from the following more detailed descriptions.

[0085] A Process Flow Diagram

[0086] In FIG. 1, a preferred process flow for isolation andpurification of monoesters such as monoglycerides according to thepresent invention is provided. The flow diagram of FIG. 1 is intended tobe representative of more generally preferred applications according tothe present invention. It is foreseen, however, that principlesaccording the to present invention may be applied in variations from theprocess schematic shown in FIG. 1.

[0087] Referring to FIG. 1, the process generally includes three stages;i.e., Stage I (reference 5); Stage II, (reference 6); and, Stage III(reference 7). In Stage I, crude monoglyceride (monoester) mixtures areprepared. In Stage II, separation of a purified monoglyceride(monoester) mixture from a raffinate or residue mixture, is conducted.In Stage III, purified monoglycerides (monoesters) are isolated from thepurified monoglyceride mixture. It is foreseen that Stages I, II and IIIcan be conducted at one facility or more than one facility; and, theycan be conducted in a batchwise or continuous process. However, it isnoted that in one particularly preferred conduct of a process accordingto the present invention, cycling of certain feeds can be utilized toadvantage. In such systems, generally the entire process will beconducted at a single facility. It may also be preferred in someapplications to develop and use equipment that can be operated in acontinuous flow-through process format, rather than a batch format, forefficiency.

[0088] 1. Stage I—Generation of Crude Glyceride Mixture

[0089] As indicated above, the first stage of the process of FIG. 1, isindicated generally at reference 5, and comprises a stage whereat thecrude glyceride mixture is generated. In general, the mixture isprepared in reactor 10. It is generated from a feed of glycerol 11 and afeed of triglyceride 12. In the reactor 10, the glycerol feed 11 andtriglyceride feed 12 are mixed, and a mixture including monoglyceride(s)and other materials, typically diglyceride(s) and triglyceride(s), isgenerated. The reactor 10 is generally operated at about 220-260° C.,and under atmospheric pressure, although a variety of conditions may beutilized. The reactor 10 may be operated in a batch manner, or as acontinuous process. Typical conventional operations for crudemonoglyceride production can be utilized, and would involve a batchoperation, with some base added as a catalyst. The typical base utilizedwill be sodium hydroxide or sodium glycollate.

[0090] The glycerol feed 11 may comprise either: an added glycerolstream from outside sources; a glycerol recycle stream from the reactor10, as described, or both. Typically glycerol feed 11 will include both:added glycerol, indicated at 15; and, a glycerol recycle stream 16, asdescribed. Streams 15 and 16 can be combined, at 17, using variousmetering techniques to obtain a preferred composition of glycerol feedin stream 11, to the reactor 10.

[0091] The triglyceride feed stream 12 may comprise an outside source(for example, natural product source) of triglyceride, cycled raffinatefrom an extraction step in Stage II, or both. Diglycerides will bepresent in the cycled raffinate and are a preferred feed component inthe triglyceride feed stream. Typically and preferably feed 12 willinclude both. It is noted that naturally occurring triglycerides, suchas palm oil or sunflower seed oil, are typically mixtures oftriglycerides. More specifically, they comprise a mixture of fats oroils including the triglycerides of numerous fatty acids.

[0092] Still referring to Stage I (reference 5), reference 25 generallyindicates the exit stream from reactor 10. Generally the exit stream 25,which comprises glycerol and a glyceride mixture, is directed intoseparator 26.

[0093] Either in separator 26, or immediately upstream, the reactoroffstream 25 is preferably cooled, for example to about 60°-120° C., andtypically the base catalyst is neutralized with an acid, usuallyphosphoric acid. Under these conditions, the glycerol will separate as aseparate phase, since it is relatively insoluble in the glyceridemixture. At 30, the glycerol phase is shown removed from separator 26.In the particular system depicted, the glycerol phase from separator 26is directed for recycling, i.e., into recycle stream 16. The crudemonoglyceride-containing fraction is shown removed from the separator26, through line 35. Thus, line 35, in combination with a remainder ofStage I, represents a source of crude monoglycerides. It is arranged fordirection of crude monoglycerides into an inlet feed of a primarycounter-current extractor, as described below.

[0094] In general, the crude monoglyceride (monoester) phase fromseparator 26 will include some residual glycerol (alcohol) therein.Preferably, before it is directed into Stage II, it is treated to reducethe residual glycerol (alcohol) presence to less than 1% by weight. Thiscan be conducted by a stripping step to remove residual glycerol.Equipment for conducting this is shown at 36. In general, any effectivestripping step/equipment may be used, although a thin film evaporator orwiped film evaporator operating under vacuum will typically bepreferred. Such stripping equipment would, of course, be useful toremove other volatile components such as free fatty acids.

[0095] At 37, an optional crude monoglyceride bleed is shown. It isforeseen that since there will be some commercial demand for the crudemonoglyceride mixture, in some systems it will be preferred to have ableed 37 so it can be drawn off (or partially drawn off), and not bedirected in Stage II, if desired.

[0096] At 40, the crude monoglyceride mixture to be purified is showndirected into Stage II (reference 6).

[0097] As explained above, a variety of methods can be used forgeneration of the crude monoesters (monoglycerides). For example, as analternative to being prepared from the reaction of glycerol withtriglycerides, a crude mixture of mono- and diglycerides can be preparedfrom the reaction of glycerol with either fatty acids or with esters offatty acids, such as methyl- and ethyl-esters. The equilibrium reactionproduct will generally comprise a crude mixture primarily ofmonoglycerides and diglycerides, with smaller amounts of triglycerides.The follow-up liquid-liquid purification process will be suitable forthese reaction products as well.

[0098] 2. Stage II—Liquid-Liquid Extraction

[0099] In general, in Stage II, crude monoglyceride is treated, througha liquid-liquid extraction, for isolation of a purified monoglyceridestream. Referring to FIG. 1, Stage II is generally indicated atreference 6. At 40, the crude monoglyceride stream is shown directedinto Stage II for processing. In general, for preferred processesaccording to the present invention, the crude monoglyceride stream 40 isgenerated from a Stage I process, as described.

[0100] Preferred processes according to the present invention areconducted in such a manner that after the crude monoester composition isdirected into Stage II, from then until isolation of the purified targetester (for example, monoester): the monoester (or other target ester) ofinterest is not distilled; the monoester (or other target ester ofinterest) is not subjected to temperatures in excess of about 140° C.;and, processes conducted under pressures greater than about 5 atm areavoided. Also in some preferred applications, no materials other thanwater, alcohol, triglyceride mixtures and similar generally recognizedas safe materials, are added or used from that point forward in theprocess. Preferably hydrocarbon solvents (propane, butane, hexanes,etc.) are avoided to advantage, or if used are used in relatively smallamounts.

[0101] In Stage II, reference 50 generally indicates the primaryextraction equipment. Typically and preferably the extraction will beconducted at 60°-80° C., to ensure that it is conducted at a temperatureabove the melting point of any triglyceride component without beingundesirably high. In general, the feed of monoglyceride mixture into theprimary extractor 50 is shown at feed line 51; and, at line 52, theraffinate, i.e., the mixture substantially depleted with respect tomonoglyceride values, is shown removed from the extractor 50. Hereinwhen it is said that the mixture is “substantially depleted” withrespect to “monoglyceride values” (or monoester values) it is meant thatthe monoglyceride (monoester) presence in the mixture has been reducedby at least 20%, due to extraction into a different phase, andseparation. Typically and preferably at least 85%, and indeed at least90% by weight of the monoester is extracted into the extractant.

[0102] At 54, the feed line for the phase into which the monoglycerideis extracted (i.e., the extractant) is shown directed into extractor 50.At 55, extractant, containing extracted monoglyceride values, is shownleaving the primary extractor 50. The material in line 55, then,comprises the liquid phase having the extracted monoglyceride valuestherein, i.e., it is a purified monoglyceride according to the presentinvention. This material is directed to Stage III, in typical processes,for separation of the monoglycerides (monoesters) from the extractant.

[0103] Still referring to FIG. 1, in Stage II (reference 6), thematerial in feed 51 to the primary extractor 50 generally and preferablycomprises: crude monoglyceride from line 40; and, triglyceride feed fromline 58. That is, prior to being directed into primary extractor 50,crude monoglyceride compositions are modified by the addition oftriglycerides thereto, and line 58 represents the source of addedtriglycerides. This will facilitate separation in the primary extractor50, since the diglyceride components of the crude monoglyceride mixturewill even more preferentially remain in the triglyceride-containingraffinate, rather than partition into the monoglyceride-containingalcohol/water phase. In typical processes, the alcohol/water feed willcomprise, by weight, about 1 times to 6 times the weight of themonoglyceride-containing stream fed into the extraction.

[0104] For the preferred system shown in FIG. 1, Stage II includes asecondary extractor 60 (or wash system). The secondary extractor 60 isused to advantage in the following manner. The offstream 55 from theprimary extractor 50 is directed into the secondary extractor 60, asindicated at inlet 61. Within the extractor 60, relatively less polarcomponents such as diglyceride component in the purified monoglyceridestream 55 are preferentially washed into the triglyceride feed ortriglyceride phase, from the alcohol/water purified monoglyceride phase(i.e., back extracted or washed). This triglyceride phase is showndirected into the secondary extractor 60 at line 65. Thus, withinsecondary extractor 60, the monoglyceride-containing alcohol/water phasefrom primary extractor 50 is extracted (or back extracted) with atriglyceride-containing phase, generating a triglyceride phase exitingextractor 60 in line 58, and an even further purified monoglyceridecontaining alcohol/water phase exiting secondary extractor 60 at 66.

[0105] In the system of FIG. 1, the triglyceride exiting the secondaryextractor 60 is fed into the primary extractor 50, and to a certainextent is even cycled into reactor 10. Referring again to Stage I, ifstill further triglyceride needs to be fed into the feed stream 12 toreactor 10, it can be added via line 67.

[0106] In the preferred arrangement shown, the crude monoglycerides areadded to Stage II downstream from the secondary extractor 60 andupstream from the primary extractor 50.

[0107] Still referring to FIG. 1, Stage II (reference 6), the exit flow52 from primary extractor 50 is shown directed into separator 70. Wateris added to separator 70, at line 71. Thus, at separator 70 an aqueousphase and an organic phase will be generated. The organic phase is shownremoved from separator 70 at line 71 a, for direction into thetriglyceride feed 12 to reactor 10. The aqueous phase is shown leavingseparator 70 at line 72, for addition into the phase used in primaryextractor 50, via line 73. This separator (which may contain more thanone stage) is used to reduce the alcohol content in stream 52.Additional reduction in alcohol and water in stream 71 a may be achievedby vaporization under vacuum.

[0108] Still referring to FIG. 1, Stage II, as indicated above, themonoglyceride enriched alcohol/water phase is shown leaving thesecondary extractor 60 at line 66, for direction into Stage III.

[0109] Herein the term “fluid direction conduit arrangement” is usedgenerally to refer to the various fluid conduits in the system fordirecting fluid flow between the various reactors, separators andextraction equipment. For example, the fluid direction conduitarrangement includes a fluid conduit 58 from the triglyceride extractantoutlet of the secondary counter-current extractor 60, to the crudemonoester composition inlet feed 51 of the primary counter-currentextractor 50; and, it also includes a fluid conduit 55 from thealcohol/water extractant outlet of the primary counter-current extractor50, into the secondary counter-current extractor inlet 61. Theseportions of the fluid direction conduit arrangement are generally foundin Stage II, FIG. 1. The term “fluid direction conduit arrangement” isintended to include within its scope any pipes, fittings, pumps, valves,or other equipment needed or desired for appropriate operation.

[0110] 3. Stage III—Monoglyceride Isolation from The Alcohol/WaterMixture

[0111] At this point, the purified monoesters are present as a solutionin aqueous alcohol. A number of options are available to recover themonoesters into a useful form (i.e., as a target ester-containing foodcomposition). For example, the aqueous alcohol/purified monoester streamcould be back extracted with a low boiling hydrocarbon, such as hexane,and the hexane could then be stripped from the monoglycerides. Therecommended hexane volume for such an operation would typically be amass flow rate at least equal to the aqueous alcohol flow rate, in orderto recover a significant portion of the monoglycerides.

[0112] An alternative method for recovery would be to cool the aqueousalcohol/monoglyceride stream to precipitate or crystallize themonoglycerides. In general, the “best” temperature for the cooled streamwould be a function of the degree of hydrogenation of themonoglycerides. Satisfactory results would typically be obtained attemperatures of about 10-30° C.

[0113] A third method for product (target ester-containing foodcomposition) recovery would be to add water to the aqueousalcohol/monoglyceride stream, reducing the solubility of themonoglycerides. Adding sufficient water to make an aqueous alcohol ofgreater than 50 vol. % water, and preferably greater than 70 vol. %water has been observed to cause separation of a significant portion ofthe monoglycerides. In general, centrifugation has been found useful forseparating the two phases after the water addition.

[0114] A still further method of product recovery is to flash or distillthe alcohol (ethanol), preferentially to the water, from the solution inorder to form a more water-rich aqueous alcohol solution, resulting ineasier separation of a monoglyceride-rich phase.

[0115] Another method to recover the product is to strip, preferablyunder vacuum, the water and alcohol (ethanol) to form a molten stream ofsubstantially pure, dry, monoglycerides. A thin film, wiped film, orscraped film evaporator would typically be preferred choice for thefinal stripping, while a shell and tube evaporator might be useful toremove the bulk of the aqueous alcohol.

[0116] A still further method to recover product would be to spray dryunder vacuum, preferably with a solid carrier such as flour or milksolids to aid in producing a granular product. Freeze drying can also bea useful technique to remove the final traces of aqueous alcohol from aconcentrated stream.

[0117] Bearing these various possibilities in mind, general referencewill be made to FIG. 1, and the isolation. From the above discussions,variations in equipment to accommodate different approaches to isolationwill be apparent.

[0118] Reference 7, FIG. 1, generally represents Stage III, i.e., thestage whereat the monoglyceride enriched (or monoester enriched)alcohol/water liquid phase is treated for isolation of monoglyceride(monoester) values therefrom, as a target ester-containing foodcomposition. In general, this phase is shown leaving the liquid-liquidextraction process, Stage II line 66, and is shown directed into StageIII, at 80. For the particular preferred system shown, in Stage III,feed 80 is directed into a distillation apparatus 81. The distillationapparatus 81 is operated to distill or vaporize the alcohol/watermixture, shown exiting at line 83, from the reactor bottoms containingpurified monoglycerides, shown leaving the distillation apparatus 81 atline 85. The distillation apparatus 81 is preferably comprised ofmultiple stages. In the first stage, the bulk of alcohol/water mixtureis preferably removed in an evaporator capable of handling a largevolatile content, such as a rising film evaporator, falling filmevaporator, shell and tube evaporator, or other equipment. Thetemperature should be maintained at 140° C. or less, preferably lessthan 100° C. at suitable pressure/vacuum for the alcohol/water mixturebeing used. Multiple effect evaporators might be used to achieve greaterenergy economy. In the later stage, the remainder of the alcohol/watermixture is removed to create a devolatilized molten product. A thin filmevaporator or wiped film evaporator is believed to be suitable for thisstage. This can be conducted with temperatures of about 140° C., andpreferably no higher than 100° C., and at pressures of 200 mm Hg orless, preferably 50 mm Hg or less. Thus, within distillation apparatus81, the monoglycerides are preferably not themselves distilled, butrather the ethanol/water solvent is distilled (or stripped) from themonoglyceride reactor bottoms. It is important to understand that inmost preferred operations of systems according to the present invention,the isolated monoglycerides are not themselves ever actually distilled.

[0119] Still referring to Stage III, FIG. 1, the ethanol/water distilledaway from the mixture, at line 83, is shown being cycled into theprimary extractor 50, Stage II. The distillation bottoms 85, containingmonoglycerides, are directed into separator 90. In separator 90, theycan be washed with water or ethanol, for further purification, andrecrystallization can be conducted, if desired. Purified monoglyceridesfrom separator 90 are removed through line 91. If desired, alcohol/wateror water utilized for separation or purification in separator 90 isshown directed via line 93, into line 94, whereat it is mixed with thedistilled ethanol/water from line 83, and is cycled into the primaryextractor 50 via line 54. In a preferred embodiment, the distillationbottoms 85 are of the desired purity and devolatilized to an extent thatthe separator 90 can be bypassed, and the distillation bottoms 85 can befurther processed, as described below for the product via line 91.

[0120] The purified monoglycerides (food composition) shown removed fromseparator 90 via line 91 can be sold as product, or further processed,for example by drying, flaking, pelletry, hydration or mixing withtriglyceride fat/oil.

[0121] From the above discussion of FIG. 1, it is apparent thatprocesses according to the present invention are particularlyadvantageous, since they are well developed for efficient operation tofacilitate generation and isolation of monoglycerides. For example, thetriglycerides added to facilitate the separation, in Stage II, arecycled into Stage I, to facilitate preparation of the monoglyceridemixture. Preferably, ethanol/water utilized as the liquid phase intowhich the partitioning of monoglyceride occurs during the liquid-liquidextractions, is cycled back into Stage II, following isolation of themonoglycerides therefrom, to advantage.

[0122] Utilization of primary and secondary extractors 50 and 60respectively, in Stage II, is unique and highly advantageous. Theextraction which occurs in secondary extractor 60 is of diglyceridesinto a triglyceride-enriched feed, and results in a fine tuning of thepurified monoglyceride stream 55, for preferred partitioning ofdiglycerides that may be present into the triglyceride feed. Thus, anydiglyceride presence, from extraction into the water/ethanol phase inextractor 50, is greatly reduced.

[0123] Line 51, directed in the primary extractor 50 includestriglyceride-enriched crude monoglyceride mixture. The term“triglyceride-enriched crude monoglyceride mixture” as used herein, inthis context, is meant to refer to a crude monoglyceride mixture towhich triglycerides have been added. (Of course, thetriglyceride-enriched crude monoglyceride mixture is itself a crudeester composition.) Preferably the triglyceride-enriched crudemonoglyceride mixture is a mixture to which there has not been anaddition of other non-alcoholic solvents, beside the triglycerides,i.e., hydrocarbon solvents such as propane, butane, hexanes, etc. Thatis, preferably the monoglyceride mixture is modified by addition theretoof triglycerides, but not by addition of other solvents, to facilitateextraction.

[0124] The triglyceride(s) generates a preferred organic phase forpartitioning and separation, in the primary extractor 50. In particular,it creates an environment in greater contrast to the alcohol/waterenvironment of the extractant, so that the diglyceride component willmore preferably remain in the organic phase, relative to partitioninginto the alcohol/water phase. Diglyceride which does partition into thealcohol/water phase, however, can be greatly removed in the secondaryextraction process. In general, then, in processes according to thepresent invention the composition of the phases in the primary extractor50 and secondary extractor 60 will be balanced to achieve a preferredefficiency of separation.

[0125] An improved system to that shown in FIG. 1 has been devised. Ingeneral, it has been observed that some of the colors and flavors fromcrude monoglycerides concentrate in the extractant phase, during theStage II extractions, and remain in the final product from Stage III.This is reasonable, given that the extractions generally will remove themonoglycerides and anything else present which is more polar than themonoglycerides. An approach has been developed to control this, which isto treat the crude monoglyceride stream with a prewash, using arelatively dilute polar solvent such as alcohol, in order to wash outsome of the impurities. Appropriate control of the alcohol content canbe used to minimize monoglyceride loss. Such a prewash would remove (orreduce the level of) undesirable components such as free fatty acids,some glycerin, catalyst residues and catalyst neutralization residues.Example 14, described hereinbelow, shows the solubility ofmonoglycerides as a function of water content in the polar phase. Withthis type of information, one can develop a suitably polar wash for thecrude monoglyceride mixture that will result in some removal of thepolar contaminants, without undesirable levels of removal ofmonoglycerides.

[0126] A flow chart depicting a system with such a wash therein isdepicted in FIG. 2. FIG. 2 is identical to FIG. 1, but for the presenceof the apparatus for the washing step shown at 138. After the wash, thecrude monoglycerides, washed for removal of some polar contaminantstherein, would be directed via line 40 into Stage II, as shown anddescribed above.

[0127] It is noted that in some instances, the stripper 36 may bereplaced with the equipment 138 for conducting the washing step. It isforeseen that a typical wash stream would be a countercurrent washcomprising a water/ethanol mix of about 44% water, 56% ethanol (by wt.).

[0128] IV. Preferred Conduct of the Extractions

[0129] In general, when processes according to the present invention arepracticed with both a primary extraction and a follow up wash step(i.e., the secondary extraction), the process may be characterized as aliquid-liquid fractionation or fractional extraction. With suchpractices, the ultimate purity obtained for the monoesters approaches100%, generally limited only by the solubility of the wash solvent(i.e., the triglycerides) in the extraction phase.

[0130] When processes according to the present invention are conductedwithout the secondary extraction, or wash step, the ultimate purityobtainable for the isolated monoesters is essentially limited by theratio of monoesters and diesters in the crude, and the selectivity, a,of the solvent. Selectivity (for monoester versus diester) is generallygiven by the formula:

α=K _(mono) /K _(di)

[0131] wherein the K's are partition coefficients (extractioncoefficients) defined as K=y/x, where y is the mass fraction of therelevant material in the extract, and x is the mass fraction of therelevant material in the raffinate phase. Of course similar formulae canbe written for selectivity of monoesters versus triester, or diesterversus triester.

[0132] For extractions involving a large number of stages, the monoesterpurity (excluding triglyceride) is given by the formula:${\% \quad {ME}} = {100 \times \left\lbrack \frac{r \times \alpha}{1 + \left( {r \times \alpha} \right)} \right\rbrack}$

[0133] wherein r=ME/DE (mass ratio) in the crude (ME being monoester, DEbeing diester). Under some typical conditions, involving monoglycerideisolation, a composition of the crude would typically be about 60 wt %monoglyceride, 35 wt % diglyceride, and 5 wt % triglyceride, giving an requal to 1.71. The required value of a to achieve a desiredmonoglyceride purity can then be calculated, with α=5.3 for 90% MG andα=11.1 for 95% MG purity. Requiring a greater than or equal to11.1limits the aqueous alcohol compositions and levels of monoglycerideswhich may be used. This is in sharp contrast to the system with a washsection, or secondary extraction, where there are no similarrestrictions on a, since the secondary extraction or wash removes orreduces undesired diglycerides from the extractant.

[0134] Thus, in general, a preferred level of purification ofmonoglycerides in preferred systems according to FIG. 1 is generallyobtained through control of:

[0135] 1. The conditions of the primary extraction;

[0136] 2. The conditions of the secondary extraction; and

[0137] 3. The relative conditions of the primary extraction and secondextraction.

[0138] In general, fatty acid esters such as monoglycerides anddiglycerides are insoluble in water but are very soluble in lowmolecular weight alcohols, i.e., C₁-C₃ alcohols such as ethanol.However, although diglycerides are somewhat soluble in aqueous ethanol,they are less so than monoglycerides. The liquid phase into which themonoglyceride is extracted in the primary extractor 50, then, ispreferably a phase comprising a mixture of alcohol and water. Themixture should be tuned to obtain a preferred amount of monoglyceridepartitioning therein, with control on a preferred maximum amount ofdiglyceride partitioning which also occurs in that stream. The amount ofdiglyceride extraction into that stream, which can be accepted, turns inpart upon the level of diglyceride removal which can be readilyconducted in the secondary extraction. The more water which is added tothe ethanol, the more specific will be the partitioning betweendiglyceride and monoglyceride in the primary extraction. That is, withan increase in water, the liquid phase into which the monoglyceride isbeing extracted has a lower propensity to also pick up (extract)diglycerides, i.e., the extraction is more selective. Of course it alsohas a lower propensity to pick up monoglycerides.

[0139] In general, it is desired to utilize conditions in whichrelatively high load of monoester (extracted ester) can be obtained. Bythis it is meant a load of at least about log (preferably at least 15 g)per 100 g extractant. Thus, it is undesirable to add so much water thatthat solubility of the monoester (extracted ester), under the extractionconditions, is below these preferred amounts. This will involve somesacrifice in purity, at least at the primary extraction stage. However,the secondary extraction or washing in preferred applications, addressesthis.

[0140] Similarly, the amount of triglycerides added (to the crude esteror crude monoglycerides) to facilitate a separation, will depend uponthe level of partitioning with respect to the diglycerides preferred.The more triglycerides added, the lower will be the propensity of thediglycerides to partition into the alcohol and the greater will be thepropensity of the diglycerides to remain in the organic(triglyceride/diglyceride) phase during the primary extraction. Thus,the level of triglycerides added can be balanced with the ethanol/watermix, to obtain a preferred partitioning of diglycerides.

[0141] A variety of extraction techniques, and extraction equipment, canbe utilized for both the primary extractor 50 and secondary extractor60. In general, counter-current extractors will be preferred, typicallyconfigured for at least two stages and more preferably at least threestages in each extraction. The choice of the number of stages is basedon the desired extend of recovery, purity and overall economics. For agiven recovery and purity, a system with more stages will allow higherloading of the extractant phase, reducing product recovery costs. In atypical and preferred system, the loading will be at least 10% byweight, monoester in the extractant. In more preferred systems, theloading will be at least 15% by weight, monoester in the extractant.

[0142] Typically, the amount of triglyceride fed into the system will bebalanced with the amount of purified monoglyceride and crudemonoglycerides removed so that the system operates at steady state withneither accumulation nor depletion. While maintaining the constraints ofmaterial balance, triglyceride can be fed into the system through eitherline 67 or line 65. In preferred embodiments, the triglyceride is fedprimarily through line 65. This maximizes the triglyceride flow throughthe extractor, diluting the diglyceride, while allowing high puritymonoglyceride production with a smaller extractant flow rate. Thisresults in higher loading and reduced product recovery costs. If theflow rate through line 37 is more than about 4 times the flow ratethrough line 66 additional triglyceride may be needed, and it can be fedthrough line 67, to obtain higher extractant loading.

[0143] V. Propylene Glycol Monoesters (PGME) and Other Monoesters

[0144] Processes as shown in FIG. 1, generally described above, can alsobe utilized to isolate other monoesters, for example propylene glycolmonoesters, using analogous techniques. In general, the feed in line 11would include propylene glycol, from line 15. Thus, the recycle at 30 in16 would be propylene glycol, and the crude mixture at line 35 wouldcomprise a mixture of propylene glycol monoester with diester and mono-,di-, and triglycerides.

[0145] In general, the preparation of propylene glycol fatty acid estersis possible from a number of routes. For example, propylene glycol andtriglycerides can be reacted together to give a reaction productcomprising primarily monoesters of propylene glycol, with lesser amountsof propylene glycol diesters, monoglycerides, diglycerides, andtriglycerides, after removal of the excess propylene glycol andglycerol. A second route is through the reaction of propylene glycolwith fatty acid or fatty acid esters, such as methyl or ethyl esters offatty acids. The product from this reaction will generally be a mixturecomprising primarily mono and di-esters of propylene glycol. A thirdroute is to react propylene oxide with fatty acid, leading to a mixtureof monoester isomers.

[0146] The proposed liquid-liquid purification process described hereinwill be useful for materials prepared at least according to the first orsecond routes. It is presently believed that the products from the firstreaction scheme would be readily separated in a stream comprisingprimarily propylene glycol monoester and monoglyceride, and, if desired,the process could be tuned to provide a stream comprising primarilypropylene glycol monoester. The reaction product from the second schemeis believed to be readily separable into a substantially pure propyleneglycol monoester stream.

[0147] As to the third approach, the monoesters are generated in asubstantially pure form.

[0148] The following may be useful, for considering a system forpurifying PGME. Typical crude PGME product, made from reacting propyleneglycol with triglycerides, would include, by weight, about 60-65% PGME;about 5-10% propylene glycol diester; about 10-15% monoglyceride; about5-9% diglyceride; and about 5-8% triglyceride. The purification approachdescribed herein would generally lead to an isolation of much of thePGME and MG values, from the remainder. It would particularly concernreductions in the diester and diglyceride amounts. The triglycerideamount may still be relatively significant, in the final isolatedmaterial. However, the material will still be preferred, due to thereduction in the presence of diglycerides.

[0149] If operated according to FIG. 1, the resulting composition wouldconsist primarily of monoglycerides and PGME, with some diglyceride. Thepropylene glycol diester and the triglycerides present in the crudemixture would be largely removed. The extractant would likely containless water than in the analogous monoglyceride purification, in order toincrease solubility of the PGME in the extractant phase. If the crudePGME product had an initial composition as reported above, it isanticipated the final product would have a composition of roughly 75-80%PGME, 15% monoglyceride, 3-6% diglyceride, less than 1% propylene glycoldiester and 2% triglyceride. To get significantly higher purity wouldrequire removal of monoglyceride. This component is more polar than thePGME and may be removed using a separation as shown in FIG. 5.

[0150] In FIG. 5, a schematic depiction of equipment and processingsteps for isolation of propylene glycol monoesters from a mixture isshown. Referring to FIG. 5, reactor 350 is a reactor in which propyleneglycol is reacted with triglyceride, to provide a mixture of propyleneglycol esters. Propylene glycol feed into reactor 350 is shown via lines351 and 352. Via line 353, a triglyceride feed into reactor 350 isshown.

[0151] The conditions of reactor 350 will be such that the propyleneglycol will be esterified by fatty acid chains of the glyceride mixture.Thus, leaving reactor 350 via line 355 will be a mixture of propyleneglycol esters and glyceride esters. It is foreseen that typicalconditions within reactor 350 will be 180-250° C., about one atmosphereof pressure or less (and generally not greater than a few atmospheres).Also, there will typically be a catalyst content in the reactor 350, forexample, typical transesterification catalysts such as sodium hydroxideor sodium glycollate, etc.

[0152] The mixture feed of line 355 is directed into a separator 356.The separator 356 will be operated as a glycol decanter, with glycerol,glycol or other immiscible materials removed via line 357, and recycledinto reactor 350. The crude ester phase, comprising propylene glycolmonoesters and diesters, as well as various glycerides, is shown removedfrom separator 356 through line 360. It is directed into stripper 361,for removal of volatiles. Stripper 361, of course, is an optional step.

[0153] The mixture of esters, removed from the stripper 361 is showndirected via line 362 into optional wash 363. In wash 363, a relativelypolar solvent, for example water or a mixture of water and ethanol, canbe applied to remove highly polar impurities from the mixture of variousesters. A similar wash was described in connection with FIG. 2, at 138.

[0154] The esters are shown removed from water wash 363 via line 364.They are eventually directed via line 365 into extractor 370. Inextractor 370, they are treated with a countercurrent extractant phasedirected in via line 371, with the extractant, containing a preferredmonoester phase therein, primarily, removed via line 372. It is foreseenthat a preferred extractant introduced via line 371 would be an aqueousalcohol mixture, preferably water/ethanol containing, by weight, 20-40%water and 60-80% alcohol.

[0155] The raffinate from extractor 370 is shown removed via line 375.The raffinate would generally contain diesters and triesters(contaminating esters), as well as the propylene glycol monoesters(target esters). That is, preferably the extraction which occurs inextractor 370 is tuned so that the material removed via line 372 is highin glyceride monoester content (one of the contaminating esters whenPGME's are the target ester), but low in propylene glycol monoester(target ester) and diester content (contaminating ester), as well as lowin diglyceride and triglyceride content (also contaminating esters).

[0156] The monoglycerides removed via line 372 are directed into thesecond extractor 386, wherein they are washed with a triglyceride washvia line 387 and are removed to monoglyceride recovery via line 388.This may be generally as described above in connection with FIGS. 1 and2, for monoglyceride recovery (Stage III). It is noted that thetriglyceride phase is shown removed from extractor 386 via line 389 andit is mixed with the crude phase to be purified, introduced via line364.

[0157] Thus far, the arrangement of FIG. 5 is generally as describedabove in connection with FIGS. 1 and 2. Similar conditions and equipmentcan be used.

[0158] Turning now to the phase removed via line 375, which contains thedesired propylene glycol monoester therein, as well as contaminatingdiester and variant glyceride diesters and triesters. It is showndirected via line 375 into line 395, and ultimately into extractor 396.In extractor 396, it is extracted with an extractant phase introducedvia line 397, with raffinate removed via line 398 and extractant phaseremoved via line 399. The extractant introduced via line 397 wouldgenerally comprise an aqueous alcohol mix, preferably a mixture of waterand ethanol as follows: 5-30% water (by wt.); and, 70-95% alcohol (bywt.).

[0159] In general, the extractant will be tuned for preferred orpreferential removal of the propylene glycol monoester, relative tovarious contaminating diesters and triesters. This can be accomplishedby adjusting: the water/alcohol content; flow rates; and, number ofextraction stages.

[0160] Still referring to FIG. 5, the extractant phase, purified inpropylene glycol monoester content relative to other contaminants, isdirected into the second separator or wash equipment 405, via line 399.Within extractor 405, the material is treated with a triglyceride washintroduced via line 406. The raffinate is removed via line 407, and isdirected into line 395. The propylene glycol monoester (target ester)containing phase is removed from extractor 405 via line 410, and isdirected to propylene glycol monoester isolation (recovery), for exampleby the various purification techniques described above in connectionwith FIG. 1, for monoglyceride isolation (recovery).

[0161] Still referring to FIG. 5, at 415 a separator for the raffinateof line 398 is shown. Line 416 can be used to introduce water, forexample, into the separator 415, in order to reduce the alcohol contentof the raffinate, similarly to separator 70, FIGS. 1 and 2. The waterwash is shown removed via line 417, with the remaining organic phase,containing triglyceride and various diesters (contaminating esters)directed via line 420, through recycling, into reactor 350. An auxiliarytriglyceride feed is shown at line 421.

[0162] It is anticipated that a system of this type could be used togive propylene glycol monoester compositions with purity of greater than85%, by weight; and preferably greater than 90%, by weight; based ontotal ester content.

[0163] VI. Some Advantageous Operations; Products

[0164] In general, the processes and techniques described herein resultin purification of target esters as food compositions. These materialscan be used as food additives, to advantage in food mixes. Typicaltarget esters isolated according to the present invention will bemonoesters such as monoglycerides or propylene glycol monoesters; or,diesters such as diglycerides.

[0165] In general, selected target esters according to the presentinvention will have wide application in the food industry. Many of thempossess characteristics rendering utility in connection with thefollowing:

[0166] 1. Operation as an emulsifier.

[0167] 2. Operation as a starch complexing agent.

[0168] 3. Operation to reinforce protein.

[0169] 4. Operation in aeration and to stabilize foam.

[0170] 5. Operation to modify fat crystallization tendencies.

[0171] More specifically, many of the target esters that can be isolatedaccording to the present invention will be effective as emulsifiers infood mixes. They can be used, for example, to stabilize water-in-oilemulsions (for example in the generation of margarines or low caloriespreads); or, in the stabilization of oil-in-water emulsions (forexample in milk emulsions or salad dressings). Monoglycerides, propyleneglycol esters, and modified monoglycerides have been widely utilized inthis manner. Generally what is required is an emulsifying (oremulsion-stabilizing) effective amount of the agent, to achieve thedesirable effect. While the most desirable amount will differ dependingupon the particular composition involved, in general the amounts ofisolated target ester materials used according to the present inventionthat will be preferred or effective, will be similar to amounts usedwith respect to emulsifying agents in previous compositions, accordingto known techniques. Some examples are provided hereinbelow.

[0172] With respect to operation as a starch complexing agent, ingeneral it has been observed that especially monoglycerides have astarch complexing effect. In operation, they are mixed into such foodmixes or dough formulations and have the effect of providing some crumbconditioning and anti-sticking properties. In general, their utilizationwill involve providing a starch complexing effective amount in a doughcomposition. They may similarly be used in food mixes for pasta productsand potato products, two other food products with high starchcompositions, for related desirable features. Examples of the use ofmonoglycerides in “starch complexing effective amounts” are providedhereinbelow.

[0173] Another manner in which target esters according to the inventionmay be used is in doughs or as dough conditioning agents, due to theirproperties to reinforce proteins. Typical preferred target esters foraccomplishment of this are the diacteyl tartaric acid esters ofmonoglyceride and ethoxylated monoglycerides and ethoxylateddiglycerides. In general as a result of protein interaction, they havebeen found, when added to bread doughs for example, to provide forhigher bake volume and desirable or preferential texture. In general,what is required is a dough conditioning effective amount or proteininteraction effective amount of the additive, to achieve the desirableimprovement in property. Typical applications to achieve this would be ause at about 0.1-0.6%, by wt., based on the bread dough flour weight.

[0174] Also as indicated above, certain selected target esters accordingto the present invention are desirable as aerating agents and foamstabilizers. Use as foam stabilizers would typically involve addition incompositions for generation of whipped toppings made from dairy creamand imitation cream. When used in this manner, they bring aboutdestabilization of fat globules to promote the formation of a good andstable foam. In general, target esters utilizable for this compriseeither the monoglycerides, modified monoglycerides or propylene glycolmonoesters. Typical preferred ones for this use are propylene glycolmonoesters, lactylated monoglycerides and acetylated monoglycerides.Typical amounts of use in whipped toppings are provided hereinbelow.

[0175] As to utilization as an aerating agent, typical applicationsinvolve use in various batters, for example cake batter, so that whenwhipped, it generates higher volume due to aeration. Monoglycerides areamong the preferred target esters, for use in these applications.Typical amounts are provided hereinbelow.

[0176] Finally, it was indicated above that target esters will in someinstances be used to modify fat crystallization tendencies. For example,the typical applications will be as additives to monoglycerides (i.e.,the target ester would be a propylene glycol ester or modifiedmonoglyceride which is then added to a monoglyceride to affect itscrystallization form or tendencies), or to modify crystallizationtendencies in such materials as chocolates containing cocoa buttersubstitutes, to affect the crystallization tendency of the substitute.Typical amounts effective to accomplish these will be varied dependingupon the specific components; however, generally not more than about 2%,by wt., in the food composition will be needed for desirable effects.

[0177] Another use of various target esters isolated according to thepresent invention is in shortenings. In general, shortenings aremixtures of edible fats processed for certain desirable characteristics,for example, preferred melting profiles or solid fat indices. Typicaltarget esters to be added to such compositions will be themonoglycerides, the diglycerides and the propylene glycol monoesters.These materials will be usable in both all purpose shortenings and alsospecialized shortenings such as shortenings targeted to specific bakerysegments. The amounts will be varied, depending on the specificshortening formulation and use. In general, amounts similar to thoseused in conventional shortenings will be acceptable and desirable.Relative to other uses of target esters described above, the amountsused in shortenings may be very high.

[0178] Sometimes processes which involve distillation of monoesters suchas monoglycerides or propylene glycol monoesters, are associated withthe generation of “off tastes” and/or “off aromas” in the final product.The specific source of these off flavors or off aromas is not presentlyknown. However, it seems to be associated with the conduct ofdistillation processes, i.e., processes that concern heating mixturescontaining the monoglyceride (or propylene glycol monoester) of interestuntil they vaporize under the distillation conditions, typically 240° C.Methods according to the present invention can be conducted in overallprocess systems wherein no distillation of the monoglyceride product(PGME product or other ester product isolated) occurs anywhere in thesystem, and in which, after Stage II is begun, the monoester (or otherester) to be purified is never subjected to temperatures above about140° C., and typically not above 100° C. This can lead to the generationof product not possessing the same extent of “off flavor” or “off odor”characteristic sometimes associated conventional processing. Inaddition, by avoiding exposure to high temperature, the product may bemore shelf stable. The processes of the most preferred systems such asshown in FIG. 1 are systems in which no distillation of themonoglyceride (or PGME) occurs.

[0179] In addition, processes according to present invention can beutilized or “tuned” to obtain preferred levels of purity for the targetester. In general, with distillation processes, the upper limit ofpurification (of monoglycerides) obtained in the commercial practice inthe past has been about 3% diglyceride residual. With extractionprocesses according to the present invention, purifications on the orderof less than 5% diglyceride residual, typically less than 3% and ofteneven less than 2% diglyceride residual can be readily obtained, ifdesired.

[0180] Again, in addition to use as an emulsifier in food systems,purified monoglycerides according to the present invention can be usedas a starting material for the production of a number of relatedemulsifiers. For example, acetylated monoglycerides, citric acid estersof monoglycerides, sodium salts of citric acid esters of monoglycerides,diacteyl tartaric acid esters of monoglycerides, and lactic acid estersof monoglycerides are all emulsifiers derived from monoglycerides. It isanticipated that preferred such materials can be prepared from purifiedmonoglycerides according to the present invention.

[0181] It is also noted that derivatives of glycerides can be purifiedfrom crude mixtures of derivatives using the same techniques describedabove for isolation of monoglycerides or diglycerides. That is, thegeneral principles of aqueous alcohol extraction and, optionally,providing a triglyceride enriched non-polar counterphase, can be appliedto the purification of derivatives. (It is noted that such derivativesare not readily purified by distillation.) It is foreseen that the mostsuited derivatives to such a process would be the acetylatedmonoglycerides, citric acid esters of monoglycerides, diacetyl tartaricacid esters of monoglycerides and lactic acid esters of monoglycerides.

[0182] Derivatives of target esters can be prepared using general,conventional, techniques. For example, lactic acid esters ofmonoglycerides are made by reacting lactic acid with the purifiedmonoglycerides. (Of course because lactic acid possesses a free hydroxylgroup available for further reaction, dimers and oligomers are possible.Thus with conventional techniques, control of the reaction may benecessary to achieve the desired mix of lactic acid esters.) Citric acidesters can analogously be manufactured by the reaction of citric acidand monoglycerides. Succinylated monoglycerides are generally thesuccinic acid ester of monoglycerides made from reacting succinicanhydride with monoglycerides. The resulting reaction mix wouldgenerally comprise monoglycerides, and mono- and di- substitutedsuccinylated monoglycerides.

[0183] Acetic acid esters of monoglycerides are generally manufacturedfrom a reaction of monoglyceride with acetic anhydride, followed bydistillation of acetic acid from the resulting mixture of monoglyceride,and mono- and di- substituted acetylated monoglycerides. Alternatively,they are made by the interesterification of triacetin, triglycerides andglycerol, which would lead to a complex mixture of mono-, di- andtriglycerides to be purified using the techniques described herein.

[0184] Diacetyl tartaric acid esters of monoglycerides are generallyformed by reaction of diacetyl tartaric acid anhydride and themonoglyceride. Again, a complex mixture can form if rearrangementoccurs, but the mixture can be appropriately purified using thetechniques described herein. Similarly to the other derivativesdescribed above, ethoxylated derivatives can be made using conventionaltechniques.

[0185] As indicated generally above, derivatives of monoglycerides wouldhave a variety of uses in the food industry, either used alone or incombination to provide emulsion stabilization, to provide improvedaeration and foam stabilization, to form complexes with starch andprevent staling and sticking, to strengthen dough to retain its rise,and to prevent changes in crystal structure during storage. Usefullevels generally range from 0.5 wt % up to 8 wt %, depending on theproduct and application. The purified monoesters provided by the presentinvention are believed to be suitable replacements for distilledmonoesters at about the same use levels. In addition, the monoesters ofthe present invention may be a cost effective replacement, in someinstance, for crude monoesters and the use level would be based oncomparable amount of monoester.

[0186] The monoesters of the present invention would be provided in asimilar form to the existing products, as a liquid or solid, bulk,powder, flake, 50 lb. cube, dry or hydrated, with or without theappropriate antioxidants, crystal habit modifiers, and carriers.

[0187] Processes according to the present invention can be operated ingenerally preferred, economic, manners, due to the recyclingcapabilities discussed above with respect to FIGS. 1-5. Also pressurizedconditions, and thus for many steps equipment associated withpressurized conditions, can be avoided. Finally, heating target estermaterial to in excess of 140° C. is generally avoided, leading to anenergy savings, and reduced formation of oxidation products and/oroff-flavors.

[0188] Processes according to the present invention are well developedfor utilization in the preparation for a variety of monoglycerides ormonoglyceride mixtures. The processes are not sensitive to whether ornot the triglyceride materials fed into the system are pure, and whetherthey are liquid, solid or a mixture thereof. The separations will beeffective under any of these conditions, and thus the techniques arewidely applicable.

[0189] In general, the processes described herein can be performed usingtriglycerides of fatty acids or fatty acid esters of any desired degreeof saturation, depending on the desired functionality of the finalproduct. Typically, products can be made with any desired degree ofhydrogenation, specified by the iodine value (IV), ranging from IV=2 orless, to IV=90 or higher, if desired. Products with a low IV (i.e., lessthan 5) are frequently used as emulsifying agents in margarine, cakeshortening and coatings for candies. They are also used in bakedproducts or in potato products. In these latter applications, theability to form a complex with amylose starch is useful to provideantistaling, crumb conditioning agent, and in whipped toppings where thefoam stabilization properties are useful. Low IV monoglycerides are alsofrequently used as starting points in the production of other emulsifierproducts, such as acetylated monoglycerides, citric acid esters ofmonoglycerides, sodium salts of citric acid esters of monoglycerides,diacetyl tartaric acid esters of monoglycerides, and lactic acid estersof monoglycerides.

[0190] The high IV (greater than 40) products are typically used when asofter or more liquid product is required. For example, an IV 40monoglyceride might be useful for icing or soft margarine, and IV 70 orIV 90monoglycerides might be used when even softer consistency isdesired.

[0191] In general, processes according to the present invention aredesigned to be operated, if desired, above the melting point of thematerials in question, thus treating the product essentially in a liquidstate. In general it is believed that this will give a process which isreadily adapted for a variety of oils of differing degrees ofsaturation. The separation is driven primarily by functionality,especially the balance between polar and nonpolar moieties. Because ofthis, the processes are believed to be applicable to either mixtures ofoils of different IVs or to oils of intermediate IV, which mayinherently include a variety of compounds, operating with or withoutcausing an undesired fractionation of the material on the basis of itsdegree of saturation. Processes which rely on melting point differences,such as fractional crystallization, are not believed to be as robust inthis sense. Instead, the separation will depend strongly on the IV ofthe material, because saturation strongly influences melting point.

[0192] With respect to iodine value (IV), it is noted that this measureof unsaturation can be measured using standard techniques, such as AOCSmethod #CD1B87, “The iodine value of fats and oils using the cyclohexanemethod”, incorporated herein by reference.

[0193] It is noted that the techniques described herein can be appliedto the purification of other polyhydric alcohols, besides glycerol orpropylene glycol, which have been partially esterified with fatty acids.For example, to separate sorbitan mono-esters from sorbitan di- ortri-esters, or to separate, at least partially, complex mixtures ofpolyglycerol esters of fatty acids. Related techniques may also beapplied to ethyoxylated products, such as polyoxyethylene sorbitanmonoesters or ethoxylated monoglycerides.

[0194] VII. Preferred Equipment

[0195] From the following examples of certain preferred equipment,general principles of the present invention and its application will beeven further understood.

[0196] For example, for the primary and secondary extractors equipmentsuch as: mixer/settler tanks; pulsed columns; baffle columns;reciprocating plate columns; Podbielniack centrifugal contactors;rotating disc contactor columns; and similar devices may be used. Suchequipment provides the required cycles of intimate contacting betweenphases, with follow-up phase separation.

[0197] For the various separators, a low shear mixing system ispreferred to reduce the likelihood of emulsion formation.

[0198] VII. Diglyceride Isolation

[0199] Diglycerides may be used as components in shortening, in someinstances at levels of 30% or more, and as fat replacers. As fatreplacers, they can be substituted for triglycerides, normally at lessthan 1 part by weight for each part triglyceride removed. Some productsin which they may be useful are low fat sour cream, fat replacement inpie crusts and baked goods, icings, and frozen ice cream or other frozendairy products.

[0200] The systems described in FIGS. 1-4 can be used to isolate apurified diglyceride stream (i.e., in these applications, thediglycerides are the target esters).

[0201] In general, the raffinate from the extraction of monoglycerides,in line 52, would comprise typically 60%, or less, by weightdiglycerides (and 3% or less, typically 1% or less, by wt.,monoglycerides), of the total glyceride component. For example, in thehypothetical commercial system described hereinbelow, the raffinatephase is reported as comprising 2,150 lbs./hr. of triglyceride, 1,330lbs./hr. diglyceride and 20 lbs/hr. monoglyceride, with small amounts ofwater and ethanol. The water and ethanol, of course, can be removed byvacuum stripping. Thus, the composition of the fat components(glycerides) by weight, based on total glycerides content, would beabout 61% triglyceride, 38% diglyceride and less than It (0.6%)monoglyceride. Of course, alternate raffinate compositions could beobtained with the system previously described, with each generallycharacterized by a high ratio of diglyceride to monoglyceride, in atriglyceride carrier. That is, the majority of the composition, byweight, would comprise triglyceride, with the remainder comprisingdiglyceride and having a high diglyceride to monoglyceride ratio.Typical diglyceride to monoglyceride ratios, by weight, in this materialof about 20:1 to 100:1 could be readily achieved, with the processingdescribed herein. If desired, even higher ratios could be obtained byincreasing the extraction of monoglyceride in the extractor 50, usingmore stages if appropriate. There is no theoretical limit to the ratioof diglyceride to monoglyceride in these compositions, and it isforeseen that ratios of 500:1 would generally be practical andachievable with available equipment.

[0202] Of course the relative amounts of diglyceride (target ester) andtriglyceride (contaminating ester) would depend upon the composition ofthe initial crude monoglyceride and the amount of triglyceride extractedand added. Diglyceride contents of about 20-60%, by weight based upontotal glycerides content, would be typical for the raffinate in line 52,FIGS. 1-3. Products in this range of compositions would be useful whereblends of triglycerides and diglycerides, with a minimum ofmonoglycerides, i.e., less than it by wt., are desired. Suchcompositions would not be readily obtainable through normal glycerideester productions, where expected compositions would generally alwayscontain at least 1% monoglyceride if the diglyceride content was 20% ormore.

[0203] Compositions containing greater than 50% diglycerides, and indeedgreater than 60% diglycerides, by weight, can be obtained. For example,the raffinate from the extraction of the process shown in FIG. 1, i.e.,removed via line 52, can be extracted with a second polar phaseextractant. Such a system is shown in FIG. 3. FIG. 3 is generallyanalogous to FIGS. 1 and 2, with like reference numerals referring tothe same or analogous steps and equipment. In FIG. 2, the raffinateremoved via line 52 from extractor 50 is directed into a secondextractor 175. Extractant feed is shown fed in via line 176 and removedvia line 177. Via line 177, then, an extractant phase containingpurified diglycerides (target ester) would be removed. It could bedirected to a recovery, not shown, generally comprising appropriateequipment for removal of solvent, etc. The raffinate from extractor 175is shown removed via line 178 and directed into separator 70.

[0204] It is foreseen that a preferred extractant composition would beabout 5-30%, by weight, water with the balance ethanol, although otherratios of water and either ethanol or other alcohols could be used. Thiswould create a generally polar solvent, in which the diglycerides(target ester) would be soluble in preference over the triglycerides(contaminating ester). In general, the extractant would contain lesswater, as a weight percent, than the extractant used to remove themonoglycerides, in order to improve loading. The extraction wouldgenerally, and preferably, be conducted in a countercurrent extractorsuch as extractor 175. Selectivities for extraction of diglycerides froma diglyceride/triglyceride mixture, in the substantial absence ofmonoglycerides, are not available. However, based on selectivitiescalculated from compositions shown in the Examples herein, a product ofcomposition of greater than 60 wt. % diglyceride with the balancetriglyceride, and with less than about 1% by wt. monoglyceride, isconsidered readily feasible. If higher purities of diglyceride aredesired, a diluent could be added to the nonpolar phase to improve theselectivity of DG/TG. For example, in the description herein of Example2, addition of hexane eliminated triglyceride in the polar phase. Ananalogous approach could be used in extractor 175.

[0205] Loading of the diglyceride in the polar phase will be reduced, inthe presence of the diluent, however. The technique described appearscapable of readily generating diglyceride concentrations of 60-80 wt. %,and perhaps as high as 90 wt. %. However, due to the low extractioncoefficient for diglycerides and aqueous alcohol (typically less than0.5), relatively high amounts of solvent feed via line 176 may beneeded.

[0206] An alternate approach is shown in FIG. 4. FIG. 4 differs fromFIGS. 1 and 2 in that line 58 is absent, and now line 258, fromextractor 60, would be directed to reactor 10 rather than extractor 50.It is foreseen that the process of this figure is particularly wellsuited to purification of mixtures containing at least four times asmuch diglycerides as triglycerides, by wt.; and that the monoglyceridesextraction would be tuned to removal of at least 85%, preferably atleast 90%, and in some instances greater than 95%, by wt., ofmonoglycerides in the composition, based on total glycerides weight.Also preferably in a process according to FIG. 4, the extraction inextractor 50 is tuned so that less than 20%, by wt., of the diglyceridesare extracted into the extractant.

[0207] Thus, FIG. 4 shows an alternate scheme using just two extractorsfor the production of both a monoglyceride stream and a diglyceridestream. The diglyceride stream is produced without need to extract itinto a polar phase. In FIG. 4, the crude monoglyceride, preferablycontaining low triglyceride, is extracted in a primary extractor with anaqueous alcohol polar phase, without addition of triglyceride.Conditions in the extractor are set to extract essentially all of themonoglyceride and only a portion of the diglyceride. For example, if a10:1 selectivity for mono/diglycerides is available, then by adjustingthe flow rates and using a large number of stages (6 or more equilibriumstages), it should be possible to extract any arbitrarily large fractionof the monoglycerides, while extracting only about 12% of thediglycerides. The raffinate would contain a high concentrate ofdiglycerides, moderate concentration of triglycerides, and a lowconcentration of monoglycerides, and would be suitable as a diglycerideconcentrated product. A typical product, starting from a crudemonoglyceride composition of 65 wt. % monoglyceride, 31 wt %diglyceride, and 4 wt. % triglyceride, will contain about 80-88 wt. %diglyceride, 0-9 wt. % monoglyceride, and 11-13 wt. % triglyceride. Theultimate purity would be limited by the triglyceride content of thecrude monoglyceride feed. However, for products in which this would notbe an issue, the approach described in connection with FIG. 4 would be apreferred method, as it requires just two extractors and does notrequire solubilizing the diglycerides into an aqueous solvent.

[0208] The polar phase, loaded with monoglycerides and some of thediglycerides, would be directed to a second extractor and contactedcountercurrently with a triglyceride stream. This would produce a polarphase with a high purity monoglyceride. The triglyceride phase, nowcontaining some diglyceride, would preferably be sent to a feed inlet ofa crude monoglyceride production unit, preferably after washing and/orstripping to remove water and alcohol.

[0209] IX. Experimental

EXAMPLE 1 Comparison of Extraction Using Aqueous Isopropanol with EitherTriglyceride Oil or Hexane as a Carrier Phase

[0210] Single stage, equilibrium experiments were performed by mixingtogether aqueous isopropanol (containing either 15 or 25% water byvolume), a less polar carrier phase of either IV 78 corn oil or hexane,and crude monoglycerides. The samples were made up into test tubes,heated in a temperature controlled water bath, and mixed. After mixing,the samples were allowed to stand in the water bath for at least 1 hourbefore sampling. Aliquots were taken of each phase, for the systemswhich formed two phases, and the aliquots were analyzed by gaschromatography after being evaporated at 110° C. in flowing nitrogen.The monoglyceride content for the samples in the table below were 2grams crude monoglyceride per 10 ml of combined solvent. Samples werealso made at 4 grams crude monoglyceride per 10 ml of combined solvent,but these did not generally result in more than a single phase. Thesolvents were added at a volume ratio of polar solvent to less polarsolvent of either 1/1 or 2/1. The initial composition of the crudemonoglycerides was approximately 60/35%/5% by weight ofmonoglyceride/diglyceride/triglyceride. The selectivity for themonoglyceride over diglycerides and selectivity for monoglycerides overtriglycerides are also reported. TABLE I Test results over diglyceridesoil as less polar phase. ¹Polar ²MG, ³DG, ⁴TG, ⁵MG, wt % ⁶DG, wt % ⁷TG,wt % ⁸Selec- ⁹Selec- Temp Water /Non- wt % wt % wt % non- non- non-tivity tivity (C.) vol % polar polar polar polar polar polar polar MG/DGMG/TG 45 15 1 42 24 34 11 17 72 2.7 8.1 45 15 2 43.6 15.6 40.8 12.6 11.476 2.5 6.4 60 15 1 48.8 13.9 37.3 8.6 10.1 81.2 4.1 12.4 60 15 2 31 13.755.3 13.1 12.1 74.8 2.1 3.2 45 25 1 64 21 15 8 16 76 6.1 40.5 45 25 264.3 13.3 22.4 9.7 10.4 79.9 5.2 23.6 60 25 1 75.1 11.4 13.5 9 14.1 76.810.3 47.5 60 25 2 66.8 16.9 16.2 10 14.3 75.7 5.7 31.2

[0211] Test results using hexane, under the same conditions, resulted insingle phase systems or in two phase systems with selectivity near 1,yielding no purification of the crude monoglycerides.

[0212] This example shows the usefulness of the system aqueousisopropanol/triglyceride for obtaining purification of monoglycerides.The selectivity of monoglyceride to diglyceride is sufficient, but theselectivity of monoglyceride to triglyceride is lower than desired. Theselectivity is higher at higher water concentration, and the preferredwater content for use with isopropanol is 25 volt or greater.

[0213] Hexane was shown to be unsuitable for use as a second phase.Other hydrocarbons are expected to behave similarly.

EXAMPLE 2 Comparison of Extraction using Aqueous Aqueous Ethanol withEither Triglyceride Oil or Hexane as Carrier Phase

[0214] Single stage, equilibrium experiments were performed by mixingtogether aqueous ethanol (containing either 25 or 35% water by volume),a less polar carrier phase of either IV 78 corn oil or hexane, and crudemonoglycerides. The samples were made up into test tubes, heated in atemperature controlled water bath, and mixed. After mixing, the sampleswere allowed to stand at least 1 hour before sampling. Aliquots weretaken of each phase, for the systems which formed two phases, and thealiquots were analyzed by gas chromatography after being evaporated at110° C. in flowing nitrogen. The monoglyceride content for the samplesin the table below were 2 or 4 grams crude monoglyceride per 10 ml ofcombined solvent. The solvents were added at a volume ratio of polarsolvent to less polar solvent of either 1/1 or 2/1. The initialcomposition of the crude monoglycerides was approximately 60%/35%/5% byweight of monoglyceride/diglyceride/triglyceride. The IV of the crudemonoglycerides was approximately 70. The selectivity of the polar phasefor monoglyceride over diglycerides, selectivity for monoglyceride ortriglyceride, and the partition coefficient for the monoglycerides arealso shown. In Tables II and III, the reports for the experiments areshown and analogous headings to those used in Table I have analogousmeanings.

[0215] This example shows the system aqueous ethanol/triglyceridespossesses the beneficial features of high monoglyceride to diglycerideselectivity, high monoglyceride to triglyceride selectivity, and a highextraction coefficient (corresponding to high loading of the extractantphase). The aqueous ethanol/hexane system has good selectivity, but verylow extraction coefficients (low loading of the extractant phase). TABLEII Test Results using Triglyceride Oil as Less Polar Phase Fat MG, DG,TG, Fat g/ml in Polar/ MG, DG, TG, wt % wt % wt % g/ml in less ¹Selec-²Selec- ³Partition Temp Water less wt % wt % wt % less less less polarpolar tivity tivity coefficient ° (C.) vol % polar polar polar polarpolar polar polar phase phase MG/DG MG/TG K (mono) 2g/10 ml 45 25 1 83.19.1 7.8 9 11.6 79.4 11.8 94 45 25 2 82.7 13.7 3.7 10.1 15.4 74.5 0.070.44 9.2 165 1.35 60 25 1 86.8 8.4 4.8 9.5 12.2 78.4 13.3 149 45 35 181.6 9.3 9.1 12.1 11.8 76.1 0.1 0.64 8.6 56 1.03 60 35 2 89 7.4 3.6 11.814.9 73.3 0.12 0.91 15.2 164 0.99 4g/10 ml 45 25 1 66.1 16 18 20.5 16.962.6 0.22 0.59 3.4 11 1.2 45 35 2 81.1 13.1 5.8 32.8 21.1 46 0.05 0.58 420 0.21 60 35 1 82.3 10.4 7.3 38.2 26.5 35.3 0.07 0.74 5.5 11 0.21

[0216] TABLE III Results Using Hexane As Less Polar Phase MG, DG, TG,Fat, Polar/ MG, DG, TG, wt % wt % wt % Fat g/ml Selec- Partition TempWater less wt % wt % wt % less less less g/ml less tivity coefficient(C.) vol % polar polar polar polar polar polar polar phase polar MG/DG K(mono) 2 g/10 ml 45 25 1 95.3  4.7 0 59.3 36.3 4.3 — — 12.4 — 60 25 192.7  7.3 0 58.8 35.5 5.7 — — 7.7 — 60 25 2 78.6 20.4 1 58 36.4 5.6 0.070.64 2.4 0.14 45 35 2 93.6  6.4 0 58.5 35.8 5.7 0.01 0.19 9 0.04 60 35 1no no no 59.5 35.2 5.3 0.01 0.43 — <0.03 data data data 4/10 mg 45 25 283.2 16.8 0 58.4 35.6 6.1 0.02 0.22 3 0.1 60 25 1 nd nd nd 59.4 35.3 5.30.01 0.47 — <0.05 45 35 1 87.8 12.2 0 60.2 35 4.7 0.01 0.26 4.2 0.03 6035 2 84.1 15.9 0 58.4 36.2 5.4 0.04 0.68 3.3 0.09

EXAMPLE 3 Extraction Using Aqueous Methanol and Triglyceride

[0217] Single stage, equilibrium experiments were performed by mixingtogether aqueous methanol (containing either 5 or 10% water by volume),a less polar carrier phase of IV 40 soybean oil, and crudemonoglycerides. The samples were made up into test tubes, heated in atemperature-controlled water bath, and mixed. After mixing, the sampleswere allowed to stand at least one hour before sampling. Aliquots weretaken of each phase, for the systems which formed two phases, and thealiquots were analyzed by gas chromatography after being evaporated at110° C. in flowing nitrogen. The monoglyceride charge for the samples inthe table below were 1 or 2 grams crude monoglyceride per 10 ml ofcombined solvent. The solvents were added at a volume ratio of polarsolvent to less polar solvent of 2/1. The initial composition of thecrude monoglycerides was approximately 60%/35%/5% by weight ofmonoglyceride/diglyceride/triglyceride. The IV of the crudemonoglycerides was approximately 70. The selectivity of the polar phasefor monoglyceride over diglycerides, the partition coefficient for themonoglycerides, and the selectivity for monoglycerides overtriglycerides are also shown. The results are reported in Table IV. InTable IV analogous headings to those used in Table I have analogousmeanings.

[0218] The example shows the high selectivity (monoglyceride overdiglyceride and monoglyceride over triglyceride) and high extractioncoefficient (high loading of the extractant phase) for the aqueousmethanol/triglyceride system. It appears to be a very feasible system.TABLE IV Results Using Aqueous Methanol and Triglyceride Loading (crudeMG, DG, TG, Fat, mono per MG, DG, TG, wt % wt % wt % Fat g/ml Selec-Partition Selec- Temp Water 10 ml wt % wt % wt % less less less g/mlless tivity coefficient tivity (C.) vol % solvent) polar polar polarpolar polar polar phase polar MG/DG K (mono) MG/TG 60 5 10 89.7 10.3 06.3 9.3 84.4 0.08 0.67 12.9 1.68 — 60 5 20 83.4 13.3 3.3 8.7 13.4 77.90.14 0.78 9.7 1.68 226 60 10 10 95 5 0 4.7 7.1 88.2 0.06 0.74 28.7 1.51— 60 10 10 82.3 7.5 10.2 14 14.9 71.1 0.11 0.82 11.7 0.8  41

EXAMPLE 4 Evaluation as Possible Use of Aqueous Butanol with Hexane

[0219] Crude monoglycerides (2 gm, IV 70) was weighed into test tubesand 5 ml of a mixture of 88 volt butanol and 13 volt water was added.The samples were gently heated to dissolve the crude monoglycerides. 5ml of hexane was added to the solution and the phases were mixed bygentle shaking. The tubes were placed into a temperature controlled bath(45° C. or 60° C.) for at least one hour. The aqueousbutanol/hexane/crude monoglyceride system was observed to form a singlephase solution and is not suitable for use in liq-liq extractionprocessing to purify monoglyceride.

EXAMPLE 5 Use of Aqueous Ethanol with Triglycerides

[0220] Crude monoglycerides (IV 70) were weighed into graduated tubesand aqueous ethanol was added (16 volt, 23 volt, or 30 volt water inethanol). IV 40 soybean oil was added and the samples were heated to 60°C., mixed, and allowed to equilibrate for at least one hour. The chargeof crude monoglyceride was either 10, 15, or 20 g/100 ml combinedsolvent phases, and the ratio of the solvent phases was either 2/1, 3/1,or 4/1 polar/less polar. Aliquots were taken and analyzed for fatcontent (residue upon evaporation) and for fat composition by GC. Theresults and calculated values of selectivity (monoglyceride todiglyceride content in polar phase over less polar phase) and extractioncoefficient (concentration of monoglycerides in polar phase divided byconcentration of monoglycerides in less polar phase) are shown in TableV below. A summary table is also given, showing the mean values forselectivity and extraction coefficient as a function of loading andwater content in the aqueous ethanol. Summary Table Charge WaterSelectivity g/100 ml vol % MG/DG K (mono) 10 16 15 2.4 10 23 14 1.5 1030 23 1.0 15 16 9 1.8 15 23 16 1.3 15 30 12 0.8 20 16 7 2.4 20 23 9 1.520 30 10 1.4 20 60 7 0.7

[0221] The result for 60% water in the aqueous ethanol is from aseparate experiment. Water loadings higher than 30 volt in ethanoltended to produce systems with more than two phases.

[0222] The results show the generally favorable characteristics of theaqueous ethanol/triglyceride system. For a given charge, increasingwater content resulted in an increased selectivity but decreasedextraction coefficient. For a given water content, the selectivitydecreases with increased monoglyceride charge. This factor supports theneed for a washing section if high loadings are to be used. TABLE VPhase Phase ratio Phase fat Charge (vol fat content (MG) (DG) (TG) Water(g crude) polar/ content (g/ml) (MG) (DG) (TG) non- non- non- in ETOH in10 ml non- (g/ml) non- polar polar polar polar polar polar Selectivity(vol %) sol polar) polar polar (%) (%) (%) (%) (%) (%) MG/DG Kmono 16 103 0.112 0.706 81.2 14.6 4.2 5.4 12.7 81.9 13.1 2.39 16 10 3 0.082 0.72984.6 12.8 2.6 3.8 10.2 86 17.7 2.50 30 10 3 0.074 0.887 93.4 6.6 0.0 7.412.5 80.1 23.9 1.05 30 10 3 0.055 0.769 92.6 7.4 0.0 6.7 12.3 81 23.00.99 16 20 3 0.194 0.759 76.0 16.7 7.3 9.2 16.5 74.3 8.2 2.11 16 20 30.224 0.650 69.2 20.0 10.8 8.9 13.5 77.6 5.2 2.68 30 20 3 0.151 0.74879.6 14.8 5.6 9.6 15.8 74.6 8.9 1.68 30 20 3 0.116 0.774 86.3 10.6 3.112.2 16.6 71.2 11.1 1.06 16 15 2 0.107 0.739 80.0 15.1 4.9 5.7 12 82.211.2 2.03 16 15 2 0.132 0.618 77.4 17.9 4.7 5.3 11.3 83.4 9.2 2.36 16 154 0.098 0.623 76.4 19.5 4.1 7.8 13.3 78.8 6.7 1.17 16 15 4 0.108 0.76375.0 20.9 4.0 6.1 12.2 81.7 7.2 1.70 30 15 2 0.071 0.833 90.5 9.5 0.09.6 11.2 79.2 11.1 0.80 30 15 2 0.069 0.888 90.9 9.1 0.0 9.2 11.1 79.712.1 0.76 30 15 4 0.065 0.705 88.9 11.1 0.0 9.7 15 75.3 12.4 0.84 23 102 0.049 0.729 88.6 11.4 0.0 5.8 7.6 86.6 10.2 1.02 23 10 2 0.070 0.72487.8 10.6 1.6 5.8 7.9 86.2 11.3 1.46 23 20 2 0.112 0.778 86.6 13.4 0.010.5 12.9 76.5 7.9 1.18 23 20 2 0.136 0.717 82.1 14.4 3.6 11.0 13.3 75.76.9 1.42 23 10 4 0.058 0.880 86.7 10.4 2.9 7.7 12.1 80.2 13.1 1.0 23 104 0.088 0.500 84.6 9.2 6.2 4.9 11.2 83.9 21.0 2.35 23 20 4 0.139 0.55379.2 14.3 6.5 14.3 18.2 67.5 7.0 1.39 23 20 4 0.127 0.691 84.9 13.5 1.68.4 17.5 74.1 13.1 1.85 23 15 3 0.098 0.784 90.3 9.7 0.0 7.9 11.6 80.413.7 1.43 23 15 3 0.111 0.683 89.9 10.1 0.0 10.3 14.9 74.8 12.9 1.42 2315 3 0.102 0.893 89.6 10.4 0.0 10.0 12.6 77.4 10.9 1.03 23 15 3 0.0910.661 92.5 7.5 0.0 7.4 14.2 78.4 23.7 1.73 23 15 3 0.094 0.738 92.3 7.70.0 8.5 14.1 77.5 19.9 1.38 23 15 3 0.099 0.768 92.3 7.7 0.0 10.6 13.975.5 15.7 1.12

EXAMPLE 6 Equilibrium Distribution at Low Diglyceride Level

[0223] A series of experiments was run to determine the equilibriumdistribution between mono-, di-, and triglycerides at moderate levels ofdiglyceride. Mixtures were made up using a triglyceride oil, distilledmonoglycerides (IV 70), and aqueous ethanol. The aqueous ethanol waseither 16, 23, or 30 volt water in ethanol. The aqueous ethanol wasadded in an amount sufficient to give a two phase system. The sampleswere mixed and equilibrated at about 65° C. Aliquots were removed andthe fat content determined by residual weight after evaporation at about110° C. in flowing nitrogen. The evaporated samples were thenderivitized and analyzed by GC to determine the monoglyceride,diglyceride, and triglyceride content. Water was determined by KarlFisher analysis and found to be about 0-3 wt % of the less polar phase.The ethanol in the less polar phase increased with increasingmonoglyceride content. Selectivity of the polar phase for monoglyceridesover diglycerides and the monoglyceride extraction factor(concentrations based on weight) are shown in the attached Table VI.

[0224] This example shows that as the fat content of the polar phaseincreases (increased loading) the amount of triglycerides entering thepolar phase also increases, eventually limiting the monoglyceridepurity. However, even at fat contents of greater than 10 wt % in thepolar phase, the triglycerides are relatively low for the aqueousethanol/triglyceride system. TABLE VI Fat Non- Non- Non- Fat contentPolar Polar Polar polar polar polar content less phase phase phase phasephase phase polar polar Selec- K (mono) MG DG TG MG DG TG phase, phase,tivity wt (wt %) (wt %) (wt %) (wt %) (wt %) (wt %) Wt % Wt % MG/DGbasis 23% Water 95.85 1.21 2.95 0.67 1.39 97.95 3 99 164.3 4.34 96.150.43 3.41 2.29 1.27 96.44 2 98 124.0 0.86 96.82 0.79 2.39 3.27 1.3195.42 10 97 49.1 3.05 98.38 0.44 1.18 4.15 1.32 94.52 5 99 71.1 1.2096.86 0.95 2.18 5.29 1.62 93.09 11 96 31.2 2.10 94.2 0.45 5.35 10.151.05 88.8 14 96 21.7 1.35 88.32 1.05 10.63 13.07 1.21 85.72 25 95 7.81.78 88.62 1.22 10.15 11.02 1.33 87.65 21 96 8.8 1.78 92.4 1.18 6.4218.63 1.31 80.06 15 94 5.5 0.79 30% Water 94.79 0.66 4.56 2.02 1.4696.52 6 98 103.8 2.87 96.94 0.98 2.08 3.31 1.22 95.48 8 98 36.5 2.3987.48 0.65 11.87 6.2 1.48 92.32 8 98 32.1 1.15 98.66 0.45 0.89 6.72 1.4191.87 5 96 46.0 0.76 97.32 0.66 2.01 7.4 1.53 91.07 8 94 30.5 1.12 95.360.79 3.85 10.25 1.65 88.1 13 93 19.4 1.30 94.78 1.16 4.06 13.89 1.8184.3 9 95 10.6 0.65 91.7 1.28 7.02 13.47 1.71 84.83 17 95 9.1 1.22 94.261.36 4.38 43.4 1.76 54.85 14 64 2.8 0.48 16% Water 95.1 0.51 4.39 1.981.18 96.83 3 97 111.1 1.49 98 0.56 1.42 3.73 1.3 94.97 7 98 61.0 1.8896.2 0.82 2.96 5.4 1.37 93.23 20 96 29.8 3.71 90.7 1.11 8.16 7.36 1.3791.27 9 95 15.2 1.17 88.6 1.12 10.23 7.99 1.47 90.54 21 94 14.6 2.4888.4 1.18 10.45 14.82 1.56 83.62 21 92 7.9 1.36 84.2 1.27 14.57 19.031.63 79.34 24 90 5.7 1.18 83 1.42 15.59 24.68 1.73 73.69 26 88 4.1 0.9980.7 1.44 17.85 25.38 1.83 72.59 29 86 4.0 1.07

EXAMPLE 7 Equilibrium Distribution at Moderate Diglyceride Level

[0225] A series of experiments was run to determine the equilibriumdistribution between mono-, di-, and triglycerides at moderate levels ofdiglyceride. Mixtures were made up using a previously extractedtriglyceride oil/crude monoglyceride mixture (to provide a low level ofmonoglycerides and moderate level of diglycerides), distilledmonoglycerides (IV 70), and aqueous ethanol. The aqueous ethanol was 23volt water in ethanol. The aqueous ethanol was added in an amountsufficient to give a two phase system. The samples were mixed andequilibrated at about 65° C. Aliquots were removed and the fat contentdetermined by residual weight after evaporation in a vacuum oven atabout 120° C. The evaporated samples were then derivitized and analyzedby GC to determine the monoglyceride, diglyceride, and triglyceridecontent. Water was determined by Karl Fisher analysis and found to beabout 0-3 wt % of the less polar phase. Ethanol, determined bydifference, was found to be 8-5 wt % of the less polar phase. Theethanol in the less polar phase increased with increasing monoglyceridecontent. Selectivity of the polar phase for monoglycerides overdiglycerides and the monoglyceride extraction factor (concentrationsbased on weight) are shown in the attached Table VII. TABLE VII Fat wt %wt % wt % Fat content wt % wt % wt % MG DG TG content wt %, Grams GramsGrams MG DG TG less less less polar less K (mono) Comp. Comp. Comp.polar polar polar polar polar polar phase polar Selec- wt #1 #2 #3 phasephase phase phase phase phase wt % phase tivity basis 85.11 0.00 25.1392.9 5.7 1.4 4.5 11.7 83.8 6.29 91.33 42.4 1.42 81.91 1.64 24.76 90.67.2 2.2 5.1 11.8 83.1 10.10 90.38 29.1 1.99 82.99 9.97 26.31 79.5 10.010.5 10.6 10.8 78.6 28.61 88.2 8.1 2.43 83.81 19.21 32.50 67.3 10.3 22.415.6 9.2 75.2 40.97 63.68 3.9 2.11 86.27 27.62 51.36 67.1 10.1 22.8 15.99.6 74.5 41.15 83.97 4.0 2.07 82.32 34.74 56.01 57.9 9.7 32.3 18.6 9.172.4 48.87 82.21 2.9 1.85 84.78 48.03 80.32 60.0 8.9 31.1 17.6 7.3 7547.64 83 2.8 1.96

[0226] These data can be used to assist in the design of a liquid-liquidextraction process.

EXAMPLE 8 Extraction of IV 2 Crude Monoglycerides Using Triglyceride andAqueous Ethanol

[0227] A single stage separation was performed by mixing 10 g of crudeglycerol monostearate (IV approximately 2, roughly 70 wt % monoglycerideand 30 wt % diglyceride) with 30 grams of a polar solvent (10 g water,20 g ethanol) and 10 grams of a triglyceride oil (fully hydrogenatedsoybean oil, IV less than about 5) at 70 C and allowing the mixture toseparate into two phases. Phase 1 weighed 34.7 g and had a fat contentof 14.7 wt %, with composition 77.4 wt % monoglyceride, and 10.5 wt %diglyceride, and 11.9 wt % triglyceride. Phase 2 weighed 15.2 grams andhad a fat content of 84.8 wt %, with a composition of 12.9 wt %monoglyceride, 17.2 wt % diglyceride, and 70 wt % triglyceride. Theseresults indicate a selectivity for the monoglyceride over diglyceride tothe polar phase of 9.8 and an extraction factor for the monoglyceridesto the polar phase of 1.04, on a weight basis. The less polar phase wasfound to contain 2.5 wt % water, and, by difference, 12.7 wt % ethanol.this experiment shows the general feasibility of purification of low IVmonoglycerides using a low IV fat.

EXAMPLE 9 Use of Multiple Triglyceride ‘Wash’ Extractions in Combinationwith Aqueous Ethanol

[0228] A four-stage batch extraction was performed by mixing 100 g crudemonoglyceride (IV 70) with 200 g ethanol and 93 g water at about 70° C.and sequentially treating with 114 g aliquots of triglyceride oil (IV40). Approximately 4-5 g of the polar phase was removed for analysisafter each extraction. Fresh triglyceride oil was used for eachextraction. Samples of the polar phase and less polar phase wereanalyzed for water content (Karl Fisher), fat content (evaporationresidue), and ethanol (by difference). The evaporated samples were thenderivitized and analyzed by GC for the monoglyceride, diglyceride, andtriglyceride content. Results are shown in Table VIII below. TABLE VIIIMono- Di- Tri- Water, Ethanol, Fat, glyceride, glyceride, glyceride,Phase wt % wt % wt % wt % wt % wt % Stage 1, polar 27.1 59.4 13.5 83.710.7 5.6 Stage 2, polar 29.1 62.1 8.8 94.1 2.6 3.3 Stage 3, polar 25.963.6 10.5 85.8 1 13.2 Stage 4, polar 31.1 62.7 6.2 87.1 0.7 12.2 Stage1, less 2.6 10.4 87 14.6 18.4 67 polar Stage 2, less 2.1 11.9 86 6.7 4.488.9 polar Stage 3, less 2.3 9.7 88 6.3 1.7 92 polar Stage 4, less 5.317.7 77 6.4 1.5 92.1 polar

[0229] Applicants believe that additional washing stages, or a countercurrent extraction apparatus, could be used to reduce the diglyceridecontent of the polar phase to any desirable level. Applicants alsobelieve that the triglyceride content of the polar phase can becontrolled through choice of the aqueous alcohol, contacting,temperature, overall fat content, or other methods.

[0230] This example shows the progressive removal of diglycerides frommonoglycerides, by washing with triglycerides.

EXAMPLE 10 Comparative Analysis of Distilled Monoglycerides

[0231] Several samples of commercially available distilledmonoglycerides were analyzed by gas chromatography to determine themonoglyceride, diglyceride, and triglyceride content (excludingglycerol, free fatty acid, and other contaminants). The results, shownin Table IX below, indicate that diglycerides are the major impurity inthe monoglycerides and are present at levels of greater than 2.9 wt %.TABLE IX Monoglyceride Diglyceride Triglyceride Sample ID wt % wt % wt %AI90NLK 95.01 3.88 1.11 AI90AB 96.12 3.13 .075 AI90PBK 93.32 5.35 1.33AI90SBK 96.43 2.91 0.65 AI IV 70 96.19 3.63 0.18 Danisco IV 40 96.993.01 0 AI90VCK 96.99 3.01 0 AI Starplex 90 96.68 3.11 0.21

EXAMPLE 11 Washing of Raffinate to Reduce Alcohol Content

[0232] A sample of raffinate was prepared by doing a single extractionof crude monoglycerides (1000 g, IV 70) with a triglyceride mix of 500 gIV 2 soybean oil and 500 g IV 70 soybean oil and an aqueous alcohol mixof 930 g distilled water and 2000 g food grade ethanol. Afterequilibration at 70° C. The phases were separated and the raffinate wasdivided into 10 gram aliquots. The aliquots were held at 70° C. andtreated as shown in Table X. The treatment reduced the ethanol contentof the raffinate, as shown in Table X. Fat content was determined byevaporation residue, water by Karl Fischer, and ethanol by difference.TABLE X Raffinate Raffinate Raffinate washed washed washed Raffinate 3times, 2 times, 1 time, before 4 ml 12 ml 25 ml washing water waterwater Fat content, wt % 88.3 96 96.3 92.4 Water, wt % 2.4 2 1.6 1.9Ethanol, wt % 9.3 2 2.1 5.7

[0233] This example shown the ability to wash the raffinate bycontacting with water, to reduce the alcohol content.

EXAMPLE 12 Product Recovery in a Wiped Film Evaporator

[0234] The aqueous alcohol/monoglyceride extract from extraction ofcrude monoglycerides of animal origin (62 wt % monoglyceride, 35 wt %diglyceride, and 3 wt % triglyceride) was pre-concentrated using arotary evaporator to a fat content of about 44 wt %. This material wasthen fed at 170 g/hr. to a lab scale wiped film evaporator, Model KDL-4from UIC, Inc., Joliet, Illinois, running at an evaporator temperatureof 76° C. and a pressure of 250 mm HG absolute. The bottoms product wascollected and volatiles were determined by evaporation at 110° C. inflowing nitrogen. The residual volatiles, water and ethanol, were lessthan 0.4 wt %.

EXAMPLE 13 GC Analytical Procedure

[0235] Fat compositions can be determined by any suitable method, forexample gas chromatography. A preferred method is to evaporate thesamples at approximately 110° C. in flowing nitrogen, or under vacuum,to remove water and alcohol. Approximately 0.4 g of sample is thendissolved in 400 microliter of chloroform and derivitized by adding 400microliter of pyridine and 200 microliter of BSTFA solution from RegisTechnologies, Inc., Morton Grove, Illinois (BSTFA isBis(trimethylsilyl)trifluoroacetamide). The sample is then analyzedusing a Hewlett Packard Model 5890 using a 1 meter capillary column,Model DBSHT from J & W. The sample is prepared for GC injection bydiluting 10 microliters of the derivitized solution with 1.5 ml of drychloroform prior to injection. The area percent figures are converted toweight percent for the monoglycerides, diglycerides, and triglyceridesusing relative response factors determined from appropriate standards.The totals are normalized to 100% for the combined mono-, di-, andtriglycerides.

EXAMPLE 14 Effective Polar Phase Composition and Extraction Coefficient;Emulsion Formation

[0236] A mixture of fats was prepared from 900 g IV 70 crudemonoglyceride and 600 g of partially hydrogenated vegetable oil. Aninitial aqueous extraction phase was prepared from 360 grams ethanol and90 grams water. This solution was contacted with 450 g of the fatmixture, which had been melted and was held at 63-70 C. The combinedmixture was stirred at 1000 rpm for 10 minutes, then allowed to settlefor 30 minutes. After settling, a small sample was taken of each phaseand analyzed for fat content and composition. After each test,additional fat mixture and additional water was added, keeping the totalamount of fat roughly equal to the combined weight of water plusethanol, while adjusting the water content of the water/ethanol phasehigher. In the table below (Table XI), the calculated water content isbased on the nominal water plus ethanol content. When the water contentwas 36 wt. % or less, the aqueous phase was on top; around 40 wt. %water, the aqueous phase and oil phase had similar density and did notphase separate; at 44 wt. % water or higher, the aqueous phase was onthe bottom; and at 52 wt. % water or higher, the oil phase was cloudyand the compositional analysis seemed to indicate an emulsion hadformed. Fat content is reported as weight % fat based on total phaseweight, MG, DG and TG are the weight percent of fat which ismonoglyceride, diglyceride or triglyceride, respectively. TABLE XI Wt %Polar Phase Less-polar phase Water % fat MG DG TG % fat MG DG TGK_(mono) K_(di) K_(tri) 20 34 60.1 18.5 21.4 74 18.2 18.3 63.4 1.52 0.460.16 24 32 65.7 17.1 17.3 74 19.1 19.2 61.8 1.49 0.39 0.12 28 29 69.715.8 14.4 78 19.5 19.8 60.7 1.33 0.3 0.09 32 27 72.6 14.6 12.8 78 20.820.2 59 1.21 0.25 0.08 36 25 70.2 13.9 15.8 76 23.7 20.2 56.2 0.97 0.230.09 44 10 70.4 11.3 18.3 68 33.2 19.5 47.3 0.31 0.09 0.06 48 4 74.8 8.716.5 73 34.7 19.6 45.7 0.12 0.02 0.02 52 2 59 12 29 75 34.1 18.2 47.70.05 0.02 0.02 56 2 50.6 14.4 35 79 35.2 19.2 45.7 0.04 0.02 0.02 62 240 17.2 42.7 81 35.2 19.3 45.5 0.03 0.02 0.02 67 2 36.8 18.2 44.9 7934.5 18.6 46.9 0.03 0.02 0.02

[0237] It is noted that the fat content of the polar phase, K_(mono),and K_(di) drop rapidly, starting at a nominal water content of 36 wt.%. At those conditions, it should be possible to wash the system andremove water soluble impurities without extracting a significant portionof the monoglycerides.

A. Hypothetical Commercial System

[0238] A commercial plant, with a capacity of about 20 million pounds ofpurified monoglyceride per year, could theoretically be set up with thefollowing flow rates. A triglyceride rich stream, with a flow rate ofabout 2165 lb./hr. triglyceride, and other components as described inthe wash extraction section, would be mixed with a crude monoglyceridestream which has a flow rate of 3900 lb./hr, consisting of 2400 lb./hr.of monoglyceride, 1350 lb./hr. diglyceride, and 150 lb./hr. oftriglyceride. The crude monogloycerides would be prepared by thereaction of diglycerides, triglycerides, and glycerin using a catalyst,such as NaOH or other bases. After the reaction, the catalyst would beneutralized and removed and the crude monoglycerides cooled. Excessglycerin would be decanted off and an evaporator would be used tofurther strip glycerin from the product. The combined stream (crudemonoglycerides and triglyceride rich stream) would be charged to one endof a countercurrent extraction train, consisting of about 4mixer/settler vessels. This extraction train would be known as theprimary extraction train. To the other end of the extraction train wouldbe charged 14,630 lb./hr. of an aqueous alcohol extractant, consistingof 10,850 lb./hr. of ethanol and 3,780 lb./hr. water. The raffinatephase, following extraction, would contain about 2115 lb./hr.triglyceride, 1330 b./hr. diglyceride, 20 lb./hr. monoglyceride, 80lb./hr. water, and 350 lb./hr. ethanol. The raffinate stream would becontacted countercurrently with 700 lb./hr. of water, to form an aqueousphase with 700 lb./hr. water and 270 lb./hr. of ethanol, which would beused as a portion of the aqueous alcohol extractant composition. Theraffinate would then be vacuum stripped to remove ethanol and water andwould be used as a feedstock to a monoglyceride production reactor.

[0239] The extractant phase, following the extraction train, wouldcontain approximately 10,850 lb./hr. ethanol, 3,780 lb./hr. water, 2,400lb./hr. monoglyceride, 350 lb./hr. diglyceride, and 200 lb./hr.triglyceride. This phase would be fed to one end of a countercurrentextraction train, containing another 4 mixer/settler stages. Thisextraction train would be used to “wash” the diglycerides from theaqueous alcohol extractant phase to further purify the monoglycerides.To the other end of the train would be fed about 2065 lb./hr. oftriglyceride. After extraction, the triglyceride rich stream would havea flow rate of about 2165 lb./hr. of triglyceride, 330 lb./hr. ofdiglyceride, 20 lb./hr. of monoglyceride, 80 lb./hr. water, and 350lb./hr. ethanol. It would preferably be used as the triglyceride richstream feed to the primary extraction train, described above. Theextractant phase, following the wash extraction stage, would have a flowrate of about 10,500 lb./hr. ethanol, 3700 lb./hr. water, 2380 lb./hr.monoglyceride, 20 lb./hr. diglyceride and 100 lb./hr. triglyceride.

[0240] The purified monoglycerides would be removed from the extractantstream. For example, a multiple stage evaporator, perhaps followed by awiped film evaporator, would be used to remove the ethanol and water toproduce a stream of molten monoglycerides, containing approximately 2380lb./hr. monoglyceride, 20 lb./hr. diglyceride, and 100 lb./hr.triglyceride.

[0241] Use of Purified Monoglycerides or Purified PGME

[0242] Purified monoesters can be used to prepare a liquid shortening,suitable for use in bread, cake batters pizza dough, and otherapplications. The liquid shortening would consist of up to about 12 wt %purified monoester, about 2-8 wt % of a solid fat with IV less thanabout 6, and the remainder would primarily be a liquid oil, such aspartially hydrogenated vegetable oil with an IV of about 90 to 140.

[0243] Purified monoesters can also be used to prepare a plasticshortening, suitable for use in cake mixes, and would contain about 2-14wt % of the purified monoester (typically PGME). For bread shortenings,the level of monoester would be higher, amounting to about 6-20 wt % ofthe shortening, to achieve a total level in the bread of about 0.2-2.5wt % monoester.

[0244] Purified monoglycerides can also be added directly to bakeryproducts. Typically the monoglyceride would be added at a rate of0.2-0.5 wt %, dry, based on flour. The monoglyceride would typically behydrated prior to use.

[0245] Purified monoglycerides, typically with IV less than about 5,could also be added directly to starch-based foods and dried potatoproducts. The use level would typically be 0.1-1.5 wt %.

[0246] Purified PGME, with an IV less than about 5, can also be used inwhipped toppings, with a use level typically of 0.5-2 wt %, and inpowdered toppings at levels of 5-10 wt %.

[0247] The purified monoglycerides are also suitable for use in makingmargarine. For example, a stick margarine or whipped hard margarine canbe made using about 0.1-0.5 wt % of purified monoglyceride (IV less thanabout 5), about 80 wt % vegetable fat (may be partially hydrogenated),about 17% water or milk, and salt, vitamins, flavor, color,antioxidants, other emulsifiers, etc. A soft margarine (tub margarine)could be made in a similar manner, but the monoglyceride level wouldpreferably be increased slightly and the IV of the monoglyceride wouldtypically be about 30-70. The vegetable fat would be largely replacedwith a partially hydrogenated vegetable oil to provide the desireddegree of softness. A liquid margarine would use a monoglyceride with anIV of 70-125 and would replace the vegetable fat with a liquid vegetableoil with just a few percent of hard fat dispersed in it (a liquidshortening).

[0248] Diet table spreads can be made using 40-75 wt % of a vegetablefat (may be partially hydrogenated), 23-58 wt % water, 0.5-1.5 wt %purified monoglyceride (IV typically 70-125), and salt, vitamins,flavor, color, antioxidants, other emulsifiers, etc. As the amount offat is reduced the amount of monoglyceride is increased. For spreadswith less than 40% fat, the monoglyceride content would typically be 1-2wt %, and for fat-free spreads the monoglyceride content would typicallybe about 2-4 wt %.

[0249] The purified monoesters, when combined with other additives, arealso suitable for ice cream production.

[0250] X. Some Variations

[0251] It is anticipated that in some applications variations of thetechniques described herein will be desirable. For example, if thetriglycerides content of the polar phase of leaving the washing step,for example in line 66, FIG. 1, is undesirably high, steps can be takento lower its content before the monoglycerides are purified or isolated.This can be done, for example, by increasing the water content,rendering the triglycerides less soluble in the polar phase. Inaddition, a non-polar solvent, such as a hydrocarbon solvent, could beused to facilitate this. It is noted that in general it is preferred toavoid hydrocarbon solvents in systems according to the present inventionbut they may find some use in such instances.

[0252] As an alternative to the approach described in the previousparagraph, one could include hydrocarbon solvents in the triglyceridesfeed in line 65, FIG. 1, going into the washing step 60. Generally, itis anticipated that if this is practiced, this system would involve lessthan 20% by weight hydrocarbon solvent, and typically 10% by weight orless, based on total weight of triglycerides plus hydrocarbon, i.e.,non-polar solvent. It is foreseen that the addition of hydrocarbonsolvents will not be preferred, since steps would need to be taken tohandle their removal. However, they may be useful to facilitate someliquid/liquid extractions in systems according to the present invention.

[0253] Also, in some options one may wish to add water or alcohol to thepolar phase as it leaves the extraction step and prior to the washingstep, for example, addition to line 55, FIG. 1. This would be done inorder to modify the polarity of the phase, thereby affecting thesolubility of diglycerides and/or triglycerides therein, during thewashing step.

[0254] It is also noted that in some systems mixed alcohols may bedesirable, as the alcohol solvent in the alcohol phase. This might beusable to fine tune the selectivities in some systems, for example.

[0255] In some systems, it may be desirable to conduct both the primaryextraction and the follow up washing in the same multi-stage extractionequipment. In such systems, the crude monoglyceride feed would occur atan intermediate location.

What is claimed is:
 1. A method of preparing a purified targetester-containing food composition; said method including steps of: (a)providing a crude ester composition at least including: (i) target esterselected from the group consisting of: (A) C₃-diol target esters offatty acids; (B) C₃-triol target esters of fatty acids; and, (C)mixtures of (i)(A) and (i)(B); and, (ii) contaminating ester selectedfrom the group consisting of: (A) C₃-diol contaminating esters of fattyacids; (B) C₃-triol contaminating esters of fatty acids; and, (C)mixtures of (ii)(A) and (ii)(B); (b) extracting the crude estercomposition of step (a) with an aqueous alcohol phase to selectivelyextract, into an extractant phase, a first one of: (i) selected targetester; and, (ii) selected contaminating ester; relative to a second oneof: (iii) selected target ester; and, (iv) selected contaminating ester;(c) treating the extractant phase from step (b) with a crudetriglyceride phase to form: (i) a purified extractant phase; and, (ii) atriglyceride phase; and, (d) separating the purified extractant phaseresulting from step (c) from the triglyceride phase resulting from step(c).
 2. A method according to claim 1 wherein: (a) said step ofproviding a crude ester composition comprises providing a crude estercomposition containing: (i) monoglyceride as the target ester; and, (ii)a mixture of triglycerides and diglycerides as contaminating ester; (b)said step of extracting comprises preferentially extracting target esterinto said extractant phase, relative to crude contaminating ester; and,(c) said step of treating comprises reducing a diglyceride presence inthe extractant phase, relative to monoglyceride presence.
 3. A methodaccording to claim 2 wherein: (a) said step of providing a crude estercomposition includes providing a crude ester composition comprising: (i)at least 20%, and no more than 70%, monoglyceride, by wt., based on atotal weight of monoglycerides, diglycerides and triglycerides, in thecrude ester composition; and, (ii) at least 15%, by wt., diglycerides,based on a total weight of monoglycerides, diglycerides andtriglycerides in the crude monoester composition; and, (b) said steps ofextracting, treating and isolating are conducted sufficiently to providea purified extractant phase having: (i) a monoglyceride presence of noless than 90%, by wt., based on a total wt. of monoglycerides,diglycerides and triglycerides in the purified extractant phase; and,(ii) a diglyceride to triglyceride weight ratio of no greater than 1:1.4. A method according to claim 3 including a step of: (a) adding a crudetriglyceride mixture to the crude ester composition prior to said stepof extracting; said step of adding a crude triglyceride being conductedsuch that the resulting composition contains more triglycerides thandiglycerides, by weight.
 5. A method according to claim 3 wherein: (a)said step of providing a crude ester composition includes providing acrude ester composition comprising at least 30%, by wt., ofmonoglycerides and at least 25%, by wt., of diglycerides, based on totalweight of monoglycerides, diglycerides and triglycerides in the crudemonoester composition.
 6. A method according to claim 4 wherein: (a)said step of extracting with an aqueous alcohol extractant comprisesextracting with extractant containing: 60% to 90% ethanol, by weight;and, 10% to 40% water, by weight.
 7. A method according to claim 6wherein: (a) said step of extracting comprises conducting a multi-stage,counter-current extraction.
 8. A method according to claim 7 wherein:(a) said steps of treating and separating together comprise conducting amulti-stage counter-current wash of the extractant phase with crudetriglyceride.
 9. A method according to claim 8 wherein: (a) said step4(a) of adding a crude triglyceride mixture to the crude estercomposition comprises adding, as the crude triglyceride mixture, atriglyceride-containing phase from said step of conducting amulti-stage, counter-current wash.
 10. A method according to claim 9including a step of: (a) isolating a purified monoglyceride product fromthe purified extractant phase.
 11. A method according to claim 10further including a step of: (a) incorporating an emulsifying effectiveamount of the purified monoglyceride product into a margarinecomposition.
 12. A method according to claim 10 further including a stepof: (a) incorporating an emulsifying effective amount of the purifiedmonoglyceride product into a shortening composition.
 13. A methodaccording to claim 10 including a step of: (a) modifying the purifiedmonoglyceride product to a derivative selected from the group consistingof: acetylated monoglycerides; citric acid esters of monoglycerides;sodium salts of citric acid esters of monoglycerides; and lactic acidesters monoglycerides.
 14. A method according to claim 1 wherein: (a)said step of providing a crude ester composition comprises providing acrude ester composition containing: (i) diglyceride as target ester;and, (ii) a mixture of monoglycerides and triglycerides as contaminatingester; and, (b) said step of extracting comprises selectively extractingmonoglyceride contaminating ester into the extractant, relative todiglyceride target ester.
 15. A method according to claim 14 includingsteps of: (a) separating the extractant phase from step (1) (b) from aphase containing diglycerides and triglycerides.
 16. A method accordingto claim 15 including a step of: (a) selectively extracting, relative totriglycerides, diglycerides from the phase resulting from step 15(a)into an aqueous alcohol extractant phase.
 17. A method according toclaim 15 including a step of: (a) incorporating an effective amount of aresulting purified diglyceride composition into shortening.
 18. A methodaccording to claim 1 wherein: (a) said step of providing a crude estercomposition comprises providing a crude ester composition containing:(i) propylene glycol monoester as target ester; (ii) monoglycerides;and, (iii) a mixture of triglycerides and diglycerides as contaminatingester; (b) said step of extracting comprises preferentially extractingtarget ester and monoglycerides into said extractant phase, relative tocontaminating ester; and, (c) said step of treating comprises reducing adiglyceride presence in the extractant phase, relative to monoglyceridepresence.
 19. A method according to claim 1 wherein: (a) said step ofproviding a crude ester composition comprises providing a crudecomposition containing: (i) propylene glycol monoester as target ester;and, (ii) mixture of monoglycerides, diglycerides and triglycerides ascontaminating ester; (b) said step 1(b) of extracting comprisespreferentially extracting monoglycerides into said extractant phase,relative to a triglyceride phase containing propylene glycol monoester,diglycerides and triglycerides; (c) said method further including: (i) astep of extracting the triglyceride phase from step 1(d) with an aqueousalcohol extractant to selectively extract propylene glycol from atriglyceride phase containing triglycerides and diglycerides; and, (ii)a step of washing the extractant phase from step 19(c)(i) with crudetriglycerides to form a purified propylene glycol monoester phase; and,(iii) a step of isolating a purified propylene glycol monoester productfrom the purified propylene glycol monoester phase of step 19(c) (ii).20. A method according to claim 19 including a step of: (a)incorporating an aerating effective amount of the purified propyleneglycol monoester from step 19(c)(iii) into a food mix.
 21. A methodaccording to claim 1 wherein: (a) said step of providing a crude estercomposition comprises providing a crude ester composition includingcitric acid esters of monoglyceride as the C₃-diol target ester.
 22. Amethod of preparing a purified diglyceride food composition from a crudeester composition containing monoglycerides, diglycerides andtriglycerides; said method including the steps of: (a) providing a crudeester composition containing at least four times as much diglycerides astriglycerides, by wt.; (b) extracting the crude ester composition ofstep (a) with an aqueous alcohol phase tuned to selectively extract,into the extractant phase, monoglycerides, to form: (i) an extractantphase; and, (ii) a diglycerides phase; and, (c) separating theextractant phase and diglycerides phases from step 21(b); (d) said stepof extracting being conducted sufficiently to extract at least 90%, bywt., of monoglycerides in the crude ester composition without extractingmore than 20%, by wt., of the diglycerides.
 23. A method according toclaim 21 including a step of: (a) incorporating an effective amount of aresulting purified diglyceride composition into shortening.